ksh

KSH(1)                       General Commands Manual                      KSH(1)



NAME
       ksh, rksh, pfksh - KornShell, a standard/restricted command and
       programming language

NOTE
       Currently, rksh and pfksh are not available on macOS / Darwin.

SYNOPSIS
       ksh [ ±abcefhiknoprstuvxBCDP ] [ -R file ] [ ±o option ] ... [ - ] [ arg
       ... ]

DESCRIPTION
       Ksh is a command and programming language that executes commands read
       from a terminal or a file.  Rksh is a restricted version of the command
       interpreter ksh; it is used to set up login names and execution
       environments whose capabilities are more controlled than those of the
       standard shell.  Rpfksh is a profile shell version of the command
       interpreter ksh; it is used to execute commands with the attributes
       specified by the user's profiles (see pfexec(1)).  See Invocation below
       for the meaning of arguments to the shell.

   Definitions.
       A metacharacter is one of the following characters:

              ;   &   (   )   ⎪   <   >   new-line   space   tab

       A blank is a tab or a space.  An identifier is a sequence of letters,
       digits, or underscores starting with a letter or underscore.  Identifiers
       are used as components of variable names.  A vname is a sequence of one
       or more identifiers separated by a . and optionally preceded by a ..
       Vnames are used as function and variable names.  A word is a sequence of
       characters from the character set defined by the current locale,
       excluding non-quoted metacharacters.

       A command is a sequence of characters in the syntax of the shell
       language.  The shell reads each command and carries out the desired
       action either directly or by invoking separate utilities.  A built-in
       command is a command that is carried out by the shell itself without
       creating a separate process.  Some commands are built-in purely for
       convenience and are not documented here.  Built-ins that cause side
       effects in the shell environment and built-ins that are found before
       performing a path search (see Execution below) are documented here.  For
       historical reasons, some of these built-ins behave differently than other
       built-ins and are called special built-ins.

   Commands.
       A simple-command is a list of variable assignments (see Variable
       Assignments below) or a sequence of blank separated words which may be
       preceded by a list of variable assignments (see Environment below).  The
       first word specifies the name of the command to be executed.  Except as
       specified below, the remaining words are passed as arguments to the
       invoked command.  The command name is passed as argument 0 (see exec(2)).
       The value of a simple-command is its exit status; 0-255 if it terminates
       normally; 256+signum if it terminates abnormally (the name of the signal
       corresponding to the exit status can be obtained via the -l option of the
       kill built-in utility).

       A pipeline is a sequence of one or more commands separated by .  The
       standard output of each command but the last is connected by a pipe(2) to
       the standard input of the next command.  Each command, except possibly
       the last, is run as a separate process; the shell waits for the last
       command to terminate.  The exit status of a pipeline is the exit status
       of the last command unless the pipefail option is enabled.  Each pipeline
       can be preceded by the reserved word !  which causes the exit status of
       the pipeline to become 0 if the exit status of the last command is non-
       zero, and 1 if the exit status of the last command is 0.

       A list is a sequence of one or more pipelines separated by ;, &, ⎪&, &&,
       or ⎪⎪, and optionally terminated by ;, &, or ⎪&.  Of these five symbols,
       ;, &, and ⎪& have equal precedence, which is lower than that of && and
       ⎪⎪.  The symbols && and ⎪⎪ also have equal precedence.  A semicolon (;)
       causes sequential execution of the preceding pipeline; an ampersand (&)
       causes asynchronous execution of the preceding pipeline (i.e., the shell
       does not wait for that pipeline to finish).  The symbol ⎪& causes
       asynchronous execution of the preceding pipeline with a two-way pipe
       established to the parent shell; the standard input and output of the
       spawned pipeline can be written to and read from by the parent shell by
       applying the redirection operators <& and >& with arg p to commands and
       by using -p option of the built-in commands read and print described
       later.  The symbol && (⎪⎪) causes the list following it to be executed
       only if the preceding pipeline returns a zero (non-zero) value.  One or
       more new-lines may appear in a list instead of a semicolon, to delimit a
       command.  The first item  of the first pipeline of a list that is a
       simple command not beginning with a redirection, and not occurring within
       a while, until, or if list, can be preceded by a semicolon.  This
       semicolon is ignored unless the showme option is enabled as described
       with the set built-in below.

       A command is either a simple-command or one of the following.  Unless
       otherwise stated, the value returned by a command is that of the last
       simple-command executed in the command.

       for vname [ in word ... ] ;do list ;done
              Each time a for command is executed, vname is set to the next word
              taken from the in word list.  If in word ...  is omitted, then the
              for command executes the do list once for each positional
              parameter that is set starting from 1 (see Parameter Expansion
              below).  Execution ends when there are no more words in the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
              The arithmetic expression expr1 is evaluated first (see Arithmetic
              evaluation below).  The arithmetic expression expr2 is repeatedly
              evaluated until it evaluates to zero and when non-zero, list is
              executed and the arithmetic expression expr3 evaluated.  If any
              expression is omitted, then it behaves as if it evaluated to 1.

       select vname [ in word ... ] ;do list ;done
              A select command prints on standard error (file descriptor 2) the
              set of words, each preceded by a number.  If in word ...  is
              omitted, then the positional parameters starting from 1 are used
              instead (see Parameter Expansion below).  The PS3 prompt is
              printed and a line is read from the standard input.  If this line
              consists of the number of one of the listed words, then the value
              of the variable vname is set to the word corresponding to this
              number.  If this line is empty, the selection list is printed
              again.  Otherwise the value of the variable vname is set to null.
              The contents of the line read from standard input is saved in the
              variable REPLY.  The list is executed for each selection until a
              break or end-of-file is encountered.  If the REPLY variable is set
              to null by the execution of list, then the selection list is
              printed before displaying the PS3 prompt for the next selection.

       case word in [ [(]pattern [ ⎪ pattern ] ... ) list ;; ] ... esac
              A case command executes the list associated with the first pattern
              that matches word.  The form of the patterns is the same as that
              used for file-name generation (see File Name Generation below).
              The ;; operator causes execution of case to terminate.  If ;& is
              used in place of ;; the next subsequent list, if any,  is
              executed.

       if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
              The list following if is executed and, if it returns a zero exit
              status, the list following the first then is executed.  Otherwise,
              the list following elif is executed and, if its value is zero, the
              list following the next then is executed.  Failing each successive
              elif list, the else list is executed.  If the if list has non-zero
              exit status and there is no else list, then the if command returns
              a zero exit status.

       while list ;do list ;done
       until list ;do list ;done
              A while command repeatedly executes the while list and, if the
              exit status of the last command in the list is zero, executes the
              do list; otherwise the loop terminates.  If no commands in the do
              list are executed, then the while command returns a zero exit
              status; until may be used in place of while to negate the loop
              termination test.

       ((expression))
              The expression is evaluated using the rules for arithmetic
              evaluation described below.  If the value of the arithmetic
              expression is non-zero, the exit status is 0, otherwise the exit
              status is 1.

       (list)
              Execute list in a separate environment.  Note, that if two
              adjacent open parentheses are needed for nesting, a space must be
              inserted to avoid evaluation as an arithmetic command as described
              above.

       { list;}
              list is simply executed.  Note that unlike the metacharacters (
              and ), { and } are reserved words and must occur at the beginning
              of a line or after a ; in order to be recognized.

       [[ expression ]]
              Evaluates expression and returns a zero exit status when
              expression is true.  See Conditional Expressions below, for a
              description of expression.

       function varname { list ;}
       varname () { list ;}
              Define a function which is referenced by varname.  A function
              whose varname contains a .  is called a discipline function and
              the portion of the varname preceding the last .  must refer to an
              existing variable.  The body of the function is the list of
              commands between { and }.  A function defined with the function
              varname syntax can also be used as an argument to the .  special
              built-in command to get the equivalent behavior as if the
              varname() syntax were used to define it.  (See Functions below.)

       namespace varname { list ;}
              Defines or uses the name space identifier and runs the commands in
              list in this name space.  (See Name Spaces below.)

       & [ name [ arg... ]  ]
              Causes subsequent list commands terminated by & to be placed in
              the background job pool name.  If name is omitted a default
              unnamed pool is used.  Commands in a named background pool may be
              executed remotely.

       time [ pipeline ]
              If pipeline is omitted the user and system time for the current
              shell and completed child processes is printed on standard error.
              Otherwise, pipeline is executed and the elapsed time as well as
              the user and system time are printed on standard error.  The
              TIMEFORMAT variable may be set to a format string that specifies
              how the timing information should be displayed.  See Shell
              Variables below for a description of the TIMEFORMAT variable.

       The following reserved words are recognized as reserved only when they
       are the first word of a command and are not quoted:

       if then else elif fi case esac for while until do done { } function
       select time [[ ]] !

   Variable Assignments.
       One or more variable assignments can start a simple command or can be
       arguments to the typeset, enum, export, or readonly special built-in
       commands as well as to other declaration commands created as types.  The
       syntax for an assignment is of the form:

       varname=word
       varname[word]=word
              No space is permitted between varname and the = or between = and
              word.

       varname=(assign_list)
              No space is permitted between varname and the =.  The variable
              varname is unset before the assignment.  An assign_list can be one
              of the following:
                      word ...
                             Indexed array assignment.
                      [word]=word ...
                             Associative array assignment.  If preceded by
                             typeset -a this will create an indexed array
                             instead.
                      assignment ...
                             Compound variable assignment.  This creates a
                             compound variable varname with sub-variables of the
                             form varname.name, where name is the name portion
                             of assignment.  The value of varname will contain
                             all the assignment elements.  Additional
                             assignments made to sub-variables of varname will
                             also be displayed as part of the value of varname.
                             If no assignments are specified, varname will be a
                             compound variable allowing subsequence child
                             elements to be defined.
                      typeset [options] assignment ...
                             Nested variable assignment.  Multiple assignments
                             can be specified by separating each of them with a
                             ;.  The previous value is unset before the
                             assignment.  Other declaration commands such as
                             readonly, enum, and other declaration commands can
                             be used in place of typeset.
                      . filename
                             Include the assignment commands contained in
                             filename.

       In addition, a += can be used in place of the = to signify adding to or
       appending to the previous value.  When += is applied to an arithmetic
       type, word is evaluated as an arithmetic expression and added to the
       current value.  When applied to a string variable, the value defined by
       word is appended to the value.  For compound assignments, the previous
       value is not unset and the new values are appended to the current ones
       provided that the types are compatible.

       The right hand side of a variable assignment undergoes all the expansion
       listed below except word splitting, brace expansion, and file name
       generation.  When the left hand side is an assignment is a compound
       variable and the right hand is the name of a compound variable, the
       compound variable on the right will be copied or appended to the compound
       variable on the left.

   Comments.
       A word beginning with # causes that word and all the following characters
       up to a new-line to be ignored.
   Aliasing.
       The first word of each command is replaced by the text of an alias if an
       alias for this word has been defined.  An alias name consists of any
       number of characters excluding metacharacters, quoting characters, file
       expansion characters, parameter expansion and command substitution
       characters, the characters / and =.  The replacement string can contain
       any valid shell script including the metacharacters listed above.  The
       first word of each command in the replaced text, other than any that are
       in the process of being replaced, will be tested for aliases.  If the
       last character of the alias value is a blank then the word following the
       alias will also be checked for alias substitution.  Aliases can be used
       to redefine built-in commands but cannot be used to redefine the reserved
       words listed above.  Aliases can be created and listed with the alias
       command and can be removed with the unalias command.
       Aliasing is performed when scripts are read, not while they are executed.
       Therefore, for an alias to take effect, the alias definition command has
       to be executed before the command which references the alias is read.
       The following aliases are compiled into the shell but can be unset or
       redefined:
                           autoload=′typeset -fu′
                           bool=′_Bool′
                           command=′command  ′
                           compound=′typeset -C′
                           fc=hist
                           float=′typeset -lE′
                           functions=′typeset -f′
                           hash=′alias -t --′
                           history=′hist -l′
                           integer=′typeset -li′
                           nameref=′typeset -n′
                           nohup=′nohup  ′
                           r=′hist -s′
                           redirect=′command exec′
                           source=′command .′
                           stop=′kill -s STOP′
                           suspend=′kill -s STOP "$$"′
                           type=′whence -v′

   Tilde Substitution.
       After alias substitution is performed, each word is checked to see if it
       begins with an unquoted .  For tilde substitution, word also refers to
       the word portion of parameter expansion (see Parameter Expansion below).
       If it does, then the word up to a / is checked to see if it matches a
       user name in the password database (See getpwname(3).)  If a match is
       found, the and the matched login name are replaced by the login
       directory of the matched user.  If no match is found, the original text
       is left unchanged.  A by itself, or in front of a /, is replaced by
       $HOME.  A followed by a + or - is replaced by the value of $PWD and
       $OLDPWD respectively.  A followed by {fd} where fd is a file descriptor
       number or the name of a variable whose value is a file descriptor, is
       replaced by a string that is the equivalent to the path name of the file
       or directory corresponding to this file descriptor.

       In addition, when expanding a variable assignment, tilde substitution is
       attempted when the value of the assignment begins with a , and when a 
       appears after a :.  The : also terminates a login name.

   Command Substitution.
       The standard output from a command list enclosed in parentheses preceded
       by a dollar sign ( $(list) ), or in a brace group preceded by a dollar
       sign ( ${ list;} ), or in a pair of grave accents (``) may be used as
       part or all of a word; trailing new-lines are removed.  In the second
       case, the { and } are treated as a reserved words so that { must be
       followed by a blank and } must appear at the beginning of the line or
       follow a ;.  In the third (obsolete) form, the string between the quotes
       is processed for special quoting characters before the command is
       executed (see Quoting below).  The command substitution $(cat file) can
       be replaced by the equivalent but faster $(<file).  The command
       substitution $(n<#) will expand to the current byte offset for file
       descriptor n.  Except for the second form, the command list is run in a
       subshell so that no side effects are possible.  For the second form, the
       final } will be recognized as a reserved word after any token.

   Arithmetic Substitution.
       An arithmetic expression enclosed in double parentheses preceded by a
       dollar sign ( $(()) ) is replaced by the value of the arithmetic
       expression within the double parentheses.

   Process Substitution.
       Each command argument of the form <(list) or >(list) will run process
       list asynchronously connected to some file in /dev/fd if this directory
       exists, or else a fifo a temporary directory.  The name of this file will
       become the argument to the command.  If the form with > is selected then
       writing on this file will provide input for list.  If < is used, then the
       file passed as an argument will contain the output of the list process.
       For example,

              paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1)
              >(process2)

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
       the results together, and sends it to the processes process1 and
       process2, as well as putting it onto the standard output.  Note that the
       file, which is passed as an argument to the command, is a UNIX pipe(2) so
       programs that expect to lseek(2) on the file will not work.

       Process substitution of the form <(list) can also be used with the <
       redirection operator which causes the output of list to be standard input
       or the input for whatever file descriptor is specified.

   Parameter Expansion.
       A parameter is a variable, one or more digits, or any of the characters
       *, @, #, ?, -, $, and !.  A variable is denoted by a vname.  To create a
       variable whose vname contains a ., a variable whose vname consists of
       everything before the last . must already exist.  A variable has a value
       and zero or more attributes.  Variables can be assigned values and
       attributes by using the typeset special built-in command.  The attributes
       supported by the shell are described later with the typeset special
       built-in command.  Exported variables pass values and attributes to the
       environment.

       The shell supports both indexed and associative arrays.  An element of an
       array variable is referenced by a subscript.  A subscript for an indexed
       array is denoted by an arithmetic expression (see Arithmetic evaluation
       below) between a [ and a ].  To assign values to an indexed array, use
       vname=(value ...) or set -A vname  value ... .  The value of all non-
       negative subscripts must be in the range of 0 through 4,194,303.  A
       negative subscript is treated as an offset from the maximum current index
       +1 so that -1 refers to the last element.  Indexed arrays can be declared
       with the -a option to typeset.  Indexed arrays need not be declared.  Any
       reference to a variable with a valid subscript is legal and an array will
       be created if necessary.

       An associative array is created with the -A option to typeset.  A
       subscript for an associative array is denoted by a string enclosed
       between [ and ].

       Referencing any array without a subscript is equivalent to referencing
       the array with subscript 0.

       The value of a variable may be assigned by writing:

              vname=value [ vname=value ] ...

       or
              vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       Attributes assigned by the typeset special built-in command apply to all
       elements of the array.  An array element can be a simple variable, a
       compound variable or an array variable.  An element of an indexed array
       can be either an indexed array or an associative array.  An element of an
       associative array can also be either.  To refer to an array element that
       is part of an array element, concatenate the subscript in brackets.  For
       example, to refer to the foobar element of an associative array that is
       defined as the third element of the indexed array, use
       ${vname[3][foobar]}
       A nameref is a variable that is a reference to another variable.  A
       nameref is created with the -n attribute of typeset.  The value of the
       variable at the time of the typeset command becomes the variable that
       will be referenced whenever the nameref variable is used.  The name of a
       nameref cannot contain a ..  When a variable or function name contains a
       ., and the portion of the name up to the first . matches the name of a
       nameref, the variable referred to is obtained by replacing the nameref
       portion with the name of the variable referenced by the nameref.  If a
       nameref is used as the index of a for loop, a name reference is
       established for each item in the list.  A nameref provides a convenient
       way to refer to the variable inside a function whose name is passed as an
       argument to a function.  For example, if the name of a variable is passed
       as the first argument to a function, the command
              typeset -n var=$1
       inside the function causes references and assignments to var to be
       references and assignments to the variable whose name has been passed to
       the function.
       If any of the floating point attributes, -E, -F, or -X, or the integer
       attribute, -i, is set for vname, then the value is subject to arithmetic
       evaluation as described below.
       Positional parameters, parameters denoted by a number, may be assigned
       values with the set special built-in command.  Parameter $0 is set from
       argument zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
              The shell reads all the characters from ${ to the matching } as
              part of the same word even if it contains braces or
              metacharacters.  The value, if any, of the parameter is
              substituted.  The braces are required when parameter is followed
              by a letter, digit, or underscore that is not to be interpreted as
              part of its name, when the variable name contains a ..  The braces
              are also required when a variable is subscripted unless it is part
              of an Arithmetic Expression or a Conditional Expression.  If
              parameter is one or more digits then it is a positional parameter.
              A positional parameter of more than one digit must be enclosed in
              braces.  If parameter is * or @, then all the positional
              parameters, starting with $1, are substituted (separated by a
              field separator character).  If an array vname with last subscript
              * @, or for index arrays of the form sub1 ..  sub2.  is used, then
              the value for each of the elements between sub1 and sub2 inclusive
              (or all elements for * and @) is substituted, separated by the
              first character of the value of IFS.
       ${#parameter}
              If parameter is * or @, the number of positional parameters is
              substituted.  Otherwise, the length of the value of the parameter
              is substituted.
       ${#vname[*]}
       ${#vname[@]}
              The number of elements in the array vname is substituted.

       ${@vname}
              Expands to the type name (See Type Variables  below) or attributes
              of the variable referred to by vname.
       ${$parameter}
              If $parameter expands to the name of a variable, this expands to
              the value of that variable.  Otherwise, it expands to the empty
              string.  It is undefined for special parameters.
       ${!vname}
              Expands to the name of the variable referred to by vname.  This
              will be vname except when vname is a name reference.
       ${!vname[subscript]}
              Expands to name of the subscript unless subscript is *, @.  or of
              the form sub1 ..  sub2.  When subscript is *, the list of array
              subscripts for vname is generated.  For a variable that is not an
              array, the value is 0 if the variable is set.  Otherwise it is
              null.  When subscript is @, same as above, except that when used
              in double quotes, each array subscript yields a separate argument.
              When subscript is of the form sub1 ..  sub2 it expands to the list
              of subscripts between sub1 and sub2 inclusive using the same
              quoting rules as @.
       ${!prefix*}
              Expands to the names of the variables whose names begin with
              prefix.
       ${parameter:-word}
              If parameter is set and is non-null then substitute its value;
              otherwise substitute word.
       ${parameter:=word}
              If parameter is not set or is null then set it to word; the value
              of the parameter is then substituted.  Positional parameters may
              not be assigned to in this way.
       ${parameter:?word}
              If parameter is set and is non-null then substitute its value;
              otherwise, print word and exit from the shell (if not
              interactive).  If word is omitted then a standard message is
              printed.
       ${parameter:+word}
              If parameter is set and is non-null then substitute word;
              otherwise substitute nothing.
       In the above, word is not evaluated unless it is to be used as the
       substituted string, so that, in the following example, pwd is executed
       only if d is not set or is null:
              print ${d:-$(pwd)}
       If the colon ( : ) is omitted from the above expressions, then the shell
       only checks whether parameter is set or not.
       ${parameter:offset:length}
       ${parameter:offset}
              Expands to the portion of the value of parameter starting at the
              character (counting from 0) determined by expanding offset as an
              arithmetic expression and consisting of the number of characters
              determined by the arithmetic expression defined by length.  In the
              second form, the remainder of the value is used.  If A negative
              offset counts backwards from the end of parameter.  Note that one
              or more blanks is required in front of a minus sign to prevent the
              shell from interpreting the operator as :-.  If parameter is * or
              @, or is an array name indexed by * or @, then offset and length
              refer to the array index and number of elements respectively.  A
              negative offset is taken relative to one greater than the highest
              subscript for indexed arrays.  The order for associate arrays is
              unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
              If the shell pattern matches the beginning of the value of
              parameter, then the value of this expansion is the value of the
              parameter with the matched portion deleted; otherwise the value of
              this parameter is substituted.  In the first form the smallest
              matching pattern is deleted and in the second form the largest
              matching pattern is deleted.  When parameter is @, *, or an array
              variable with subscript @ or *, the substring operation is applied
              to each element in turn.

       ${parameter%pattern}
       ${parameter%%pattern}
              If the shell pattern matches the end of the value of parameter,
              then the value of this expansion is the value of the parameter
              with the matched part deleted; otherwise substitute the value of
              parameter.  In the first form the smallest matching pattern is
              deleted and in the second form the largest matching pattern is
              deleted.  When parameter is @, *, or an array variable with
              subscript @ or *, the substring operation is applied to each
              element in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
              Expands parameter and replaces the longest match of pattern with
              the given string.  Each occurrence of \n in string is replaced by
              the portion of parameter that matches the n-th sub-pattern.  In
              the first form, only the first occurrence of pattern is replaced.
              In the second form, each match for pattern is replaced by the
              given string.  The third form restricts the pattern match to the
              beginning of the string while the fourth form restricts the
              pattern match to the end of the string.  When string is null, the
              pattern will be deleted and the / in front of string may be
              omitted.  When parameter is @, *, or an array variable with
              subscript @ or *, the substitution operation is applied to each
              element in turn.  In this case, the string portion of word will be
              re-evaluated for each element.

       ${parameter^pattern}
       ${parameter^^pattern}
       ${parameter,pattern}
       ${parameter,,pattern}
              Case  modification.   This expansion modifies the case of
              alphabetic characters in parameter.  The pattern is expanded to
              produce a  pattern just as in pathname expansion.  The ^ operator
              converts lowercase characters matching pattern to uppercase.  The
              , operator converts matching uppercase characters to lowercase.
              The ^^ and ,, expansions  convert  all  matched  character  in
              the expanded  value.  The  ^ and , expansions match and convert
              only the first character in the expanded value.  If pattern is
              omitted it is treated like a ?, which matches every character.  If
              parameter is @ or *, or an array subscripted by @ or *, the case
              modification operation is  applied to each element.


       The following parameters are automatically set by the shell:
              #      The number of positional parameters in decimal.
              -      Options supplied to the shell on invocation or by the set
                     command.
              ?      The decimal value returned by the last executed command.
              $      The process number of this shell.
              _      Initially, the value of _ is an absolute pathname of the
                     shell or script being executed as passed in the
                     environment.  Subsequently it is assigned the last argument
                     of the previous command.  This parameter is not set for
                     commands which are asynchronous.  This parameter is also
                     used to hold the name of the matching MAIL file when
                     checking for mail.  While defining a compound variable or a
                     type, _ is initialized as a reference to the compound
                     variable or type.  When a discipline function is invoked, _
                     is initialized as a reference to the variable associated
                     with the call to this function.  Finally when _ is used as
                     the name of the first variable of a type definition, the
                     new type is derived from the type of the first variable
                     (See Type Variables  below.).
              !      The process id or the pool name and job number of the last
                     background command invoked or the most recent job put in
                     the background with the bg built-in command.  Background
                     jobs started in a named pool will be in the form
                     pool.number where pool is the pool name and number is the
                     job number within that pool.
              .sh.command
                     When processing a DEBUG trap, this variable contains the
                     current command line that is about to run.
              .sh.edchar
                     This variable contains the value of the keyboard character
                     (or sequence of characters if the first character is an
                     ESC, ascii 033) that has been entered when processing a
                     KEYBD trap (see Key Bindings below).  If the value is
                     changed as part of the trap action, then the new value
                     replaces the key (or key sequence) that caused the trap.
              .sh.edcol
                     The character position of the cursor at the time of the
                     most recent KEYBD trap.
              .sh.edmode
                     The value is set to ESC when processing a KEYBD trap while
                     in vi insert mode.  (See Vi Editing Mode  below.)
                     Otherwise, .sh.edmode is null when processing a KEYBD trap.
              .sh.edtext
                     The characters in the input buffer at the time of the most
                     recent KEYBD trap.  The value is null when not processing a
                     KEYBD trap.
              .sh.file
                     The pathname of the file than contains the current command.
              .sh.fun
                     The name of the current function that is being executed.
              .sh.level
                     Set to the current function depth.  This can be changed
                     inside a DEBUG trap and will set the context to the
                     specified level.
              .sh.lineno
                     Set during a DEBUG trap to the line number for the caller
                     of each function.
              .sh.match
                     An indexed array which stores the most recent match and
                     sub-pattern matches after conditional pattern matches that
                     match and after variables expansions using the operators #,
                     %, or /.  The 0-th element stores the complete match and
                     the i-th.  element stores the i-th submatch.  For // the
                     array is two dimensional with the first subscript
                     indicating the most recent match and sub-pattern match and
                     the second script indicating which match with 0
                     representing the first match.  The .sh.match variable
                     becomes unset when the variable that has expanded is
                     assigned a new value.
              .sh.math
                     Used for defining arithmetic functions (see Arithmetic
                     evaluation below).  and stores the list of user defined
                     arithmetic functions.
              .sh.name
                     Set to the name of the variable at the time that a
                     discipline function is invoked.
              .sh.op_astbin
                     The directory where several shell built-in commands are
                     bound to.  The default is /opt/ast/bin.  When the value is
                     /bin, then builtins will be bound to /bin or /usr/bin
                     depending on where the executable is found.  This variable
                     can be set by including it in the SH_OPTIONS variable.
              .sh.pgrp
                     The current process group of this shell.
              .sh.pwdfd
                     The file descriptor number for the present working
                     directory.
              .sh.sig
                     Set when executing a trap to the information contained in
                     the siginfo_t structure (See siginfo(2) for a description
                     of this structure.)
              .sh.subscript
                     Set to the name subscript of the variable at the time that
                     a discipline function is invoked.
              .sh.subshell
                     The current depth for subshells and command substitution.
              .sh.value
                     Set to the value of the variable at the time that the set
                     or append discipline function is invoked.  When a user
                     defined arithmetic function is invoked, the value of
                     .sh.value is saved and .sh.value is set to long double
                     precision floating point.  .sh.value is restored when the
                     function returns.
              .sh.version
                     Set to a value that identifies the version of this shell.
              KSH_VERSION
                     A name reference to .sh.version.
              LINENO The current line number within the script or function being
                     executed.
              OLDPWD The previous working directory set by the cd command.
              OPTARG The value of the last option argument processed by the
                     getopts built-in command.
              OPTIND The index of the last option argument processed by the
                     getopts built-in command.
              PPID   The process number of the parent of the shell.
              PWD    The present working directory set by the cd command.
              RANDOM Each time this variable is referenced, a random integer,
                     uniformly distributed between 0 and 32767, is generated.
                     The sequence of random numbers can be initialized by
                     assigning a numeric value to RANDOM.
              REPLY  This variable is set by the select statement and by the
                     read built-in command when no arguments are supplied.
              SECONDS
                     Each time this variable is referenced, the number of
                     seconds since shell invocation is returned.  If this
                     variable is assigned a value, then the value returned upon
                     reference will be the value that was assigned plus the
                     number of seconds since the assignment.
              SHLVL  An integer variable the is incremented each time the shell
                     is invoked and is exported.  If SHLVL is not in the
                     environment when the shell is invoked, it is set to 1.

       The following variables are used by the shell:
              CDPATH The search path for the cd command.
              COLUMNS
                     If this variable is set, the value is used to define the
                     width of the edit window for the shell edit modes and for
                     printing select lists.
              EDITOR If the VISUAL variable is not set, the value of this
                     variable will be checked for the patterns as described with
                     VISUAL below and the corresponding editing option (see
                     Special Command set below) will be turned on.
              ENV    If this variable is set, then parameter expansion, command
                     substitution, and arithmetic substitution are performed on
                     the value to generate the pathname of the script that will
                     be executed when the shell is invoked interactively (see
                     Invocation below).  This file is typically used for alias
                     and function definitions.  The default value is
                     $HOME/.kshrc.  On systems that support a system wide
                     /etc/ksh.kshrc initialization file, if the filename
                     generated by the expansion of ENV begins with /./ or ././
                     the system wide initialization file will not be executed.
              FCEDIT Obsolete name for the default editor name for the hist
                     command.  FCEDIT is not used when HISTEDIT is set.
              FIGNORE
                     A pattern that defines the set of filenames that will be
                     ignored when performing filename matching.
              FPATH  The search path for function definitions.  The directories
                     in this path are searched for a file with the same name as
                     the function or command when a function with the -u
                     attribute is referenced and when a command is not found.
                     If an executable file with the name of that command is
                     found, then it is read and executed in the current
                     environment.  Unlike PATH, the current directory must be
                     represented explicitly by .  rather than by adjacent :
                     characters or a beginning or ending :.
              HISTCMD
                     Number of the current command in the history file.
              HISTEDIT
                     Name for the default editor name for the hist command.
              HISTFILE
                     If this variable is set when the shell is invoked, then the
                     value is the pathname of the file that will be used to
                     store the command history (see Command Re-entry below).
              HISTSIZE
                     If this variable is set when the shell is invoked, then the
                     number of previously entered commands that are accessible
                     by this shell will be greater than or equal to this number.
                     The default is 512.
              HOME   The default argument (home directory) for the cd command.
              IFS    Internal field separators, normally space, tab, and new-
                     line that are used to separate the results of command
                     substitution or parameter expansion and to separate fields
                     with the built-in command read.  The first character of the
                     IFS variable is used to separate arguments for the "$*"
                     substitution (see Quoting below).  Each single occurrence
                     of an IFS character in the string to be split, that is not
                     in the isspace character class, and any adjacent characters
                     in IFS that are in the isspace character class, delimit a
                     field.  One or more characters in IFS that belong to the
                     isspace character class, delimit a field.  In addition, if
                     the same isspace character appears consecutively inside
                     IFS, this character is treated as if it were not in the
                     isspace class, so that if IFS consists of two tab
                     characters, then two adjacent tab characters delimit a null
                     field.
              JOBMAX This variable defines the maximum number running background
                     jobs that can run at a time.  When this limit is reached,
                     the shell will wait for a job to complete before staring a
                     new job.
              LANG   This variable determines the locale category for any
                     category not specifically selected with a variable starting
                     with LC_ or LANG.
              LC_ALL This variable overrides the value of the LANG variable and
                     any other LC_ variable.
              LC_COLLATE
                     This variable determines the locale category for character
                     collation information.
              LC_CTYPE
                     This variable determines the locale category for character
                     handling functions.  It determines the character classes
                     for pattern matching (see File Name Generation below).
              LC_NUMERIC
                     This variable determines the locale category for the
                     decimal point character.
              LINES  If this variable is set, the value is used to determine the
                     column length for printing select lists.  Select lists will
                     print vertically until about two-thirds of LINES lines are
                     filled.
              MAIL   If this variable is set to the name of a mail file and the
                     MAILPATH variable is not set, then the shell informs the
                     user of arrival of mail in the specified file.
              MAILCHECK
                     This variable specifies how often (in seconds) the shell
                     will check for changes in the modification time of any of
                     the files specified by the MAILPATH or MAIL variables.  The
                     default value is 600 seconds.  When the time has elapsed
                     the shell will check before issuing the next prompt.
              MAILPATH
                     A colon ( : ) separated list of file names.  If this
                     variable is set, then the shell informs the user of any
                     modifications to the specified files that have occurred
                     within the last MAILCHECK seconds.  Each file name can be
                     followed by a ?  and a message that will be printed.  The
                     message will undergo parameter expansion, command
                     substitution, and arithmetic substitution with the variable
                     $_ defined as the name of the file that has changed.  The
                     default message is you have mail in $_.
              PATH   The search path for commands (see Execution below).  The
                     user may not change PATH if executing under rksh (except in
                     .profile).
              PS1    The value of this variable is expanded for parameter
                     expansion, command substitution, and arithmetic
                     substitution to define the primary prompt string which by
                     default is ``$ ''.  The character !  in the primary prompt
                     string is replaced by the command number (see Command Re-
                     entry below).  Two successive occurrences of !  will
                     produce a single !  when the prompt string is printed.
              PS2    Secondary prompt string, by default ``> ''.
              PS3    Selection prompt string used within a select loop, by
                     default ``#? ''.
              PS4    The value of this variable is expanded for parameter
                     evaluation, command substitution, and arithmetic
                     substitution and precedes each line of an execution trace.
                     By default, PS4 is ``+ ''.  In addition when PS4 is unset,
                     the execution trace prompt is also ``+ ''.
              SH_OPTIONS
                     The value consists of blank separated name=value words.
                     For each name that is the name of a known option the
                     variable .sh.opt_name is assigned value.  Currently the
                     only valid option name is astbin.
              SHELL  The pathname of the shell is kept in the environment.  At
                     invocation, if the basename of this variable is rsh, rksh,
                     or krsh, then the shell becomes restricted.  If it is pfsh
                     or pfksh, then the shell becomes a profile shell (see
                     pfexec(1)).
              TIMEFORMAT
                     The value of this parameter is used as a format string
                     specifying how the timing information for pipelines
                     prefixed with the time reserved word should be displayed.
                     The % character introduces a format sequence that is
                     expanded to a time value or other information.  The format
                     sequences and their meanings are as follows.
                     %%        A literal %.
                     %[p][l]R  The elapsed time in seconds.
                     %[p][l]U  The number of CPU seconds spent in user mode.
                     %[p][l]S  The number of CPU seconds spent in system mode.
                     %[p][l]C  The total number of CPU seconds; i.e., the sum of
                               the time spent in user plus system mode.
                     %P        The CPU percentage (i.e., CPU utilization),
                               computed as C / R.

                     The brackets denote optional portions.  The optional p is a
                     digit specifying the precision, the number of fractional
                     digits after a decimal point.  A value of 0 causes no
                     decimal point or fraction to be output.  At most three
                     places after the decimal point can be displayed; values of
                     p greater than 3 are treated as 3.  If p is not specified,
                     the value 3 is used.

                     The optional l specifies a longer format, including hours
                     if greater than zero, minutes, and seconds of the form
                     HHhMMmSS.FFs.  The value of p determines whether or not the
                     fraction is included.

                     All other characters are output without change and a
                     trailing newline is added.  If unset, the default value,
                     $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS', is used.  If the
                     value is null, no timing information is displayed.

              TMOUT  If set to a value greater than zero, TMOUT will be the
                     default timeout value for the read built-in command.  The
                     select compound command terminates after TMOUT seconds when
                     input is from a terminal.  Otherwise, the shell will
                     terminate if a line is not entered within the prescribed
                     number of seconds while reading from a terminal.  (Note
                     that the shell can be compiled with a maximum bound for
                     this value which cannot be exceeded.)

              VISUAL If the value of this variable matches the pattern
                     *[Vv][Ii]*, then the vi option (see Special Command set
                     below) is turned on.  If the value matches the pattern
                     *gmacs* , the gmacs option is turned on.  If the value
                     matches the pattern *macs*, then the emacs option will be
                     turned on.  The value of VISUAL overrides the value of
                     EDITOR.

       The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
       FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set at
       all by the shell (although HOME is set by login(1)).  On some systems
       MAIL and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command substitution, the results of
       substitutions are scanned for the field separator characters (those found
       in IFS) and split into distinct fields where such characters are found.
       Explicit null fields ("" or ′′) are retained.  Implicit null fields
       (those resulting from parameters that have no values or command
       substitutions with no output) are removed.

       If the braceexpand (-B) option is set then each of the fields resulting
       from IFS are checked to see if they contain one or more of the brace
       patterns {*,*}, {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} , or
       {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are letters
       and n1,n2,n3 are signed numbers and fmt is a format specified as used by
       printf.  In each case, fields are created by prepending the characters
       before the { and appending the characters after the } to each of the
       strings generated by the characters between the { and }.  The resulting
       fields are checked to see if they have any brace patterns.

       In the first form, a field is created for each string between { and ,,
       between , and ,, and between , and }.  The string represented by * can
       contain embedded matching { and } without quoting.  Otherwise, each { and
       } with * must be quoted.

       In the seconds form, l1 and l2 must both be either upper case or both be
       lower case characters in the C locale.  In this case a field is created
       for each character from l1 thru l2.

       In the remaining forms, a field is created for each number starting at n1
       and continuing until it reaches n2 incrementing n1 by n3.  The cases
       where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1
       otherwise.  If forms which specify %fmt any format flags, widths and
       precisions can be specified and fmt can end in any of the specifiers
       cdiouxX.  For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8 fields,
       a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z4cx.

   File Name Generation.
       Following splitting, each field is scanned for the characters *, ?, (,
       and [ unless the -f option has been set.  If one of these characters
       appears, then the word is regarded as a pattern.  Each file name
       component that contains any pattern character is replaced with a
       lexicographically sorted set of names that matches the pattern from that
       directory.  If no file name is found that matches the pattern, then that
       component of the filename is left unchanged unless the pattern is
       prefixed with ∼(N) in which case it is removed as described below.  If
       FIGNORE is set, then each file name component that matches the pattern
       defined by the value of FIGNORE is ignored when generating the matching
       filenames.  The names .  and ..  are also ignored.  If FIGNORE is not
       set, the character .  at the start of each file name component will be
       ignored unless the first character of the pattern corresponding to this
       component is the character .  itself.  Note, that for other uses of
       pattern matching the / and .  are not treated specially.

              *      Matches any string, including the null string.  When used
                     for filename expansion, if the globstar option is on, an
                     isolated pattern of two adjacent *'s will match all files
                     and zero or more directories and subdirectories.  If
                     followed by a / then only directories and subdirectories
                     will match.
              ?      Matches any single character.
              [...]  Matches any one of the enclosed characters.  A pair of
                     characters separated by - matches any character lexically
                     between the pair, inclusive.  If the first character
                     following the opening [ is a !  or ^ then any character not
                     enclosed is matched.  A - can be included in the character
                     set by putting it as the first or last character.
                     Within [ and ], character classes can be specified with the
                     syntax [:class:] where class is one of the following
                     classes defined in the ANSI-C standard: (Note that word is
                     equivalent to alnum plus the character _.)
                     alnum alpha blank cntrl digit graph lower print punct space
                     upper word xdigit
                     Within [ and ], an equivalence class can be specified with
                     the syntax [=c=] which matches all characters with the same
                     primary collation weight (as defined by the current locale)
                     as the character c.  Within [ and ], [.symbol.]  matches
                     the collating symbol symbol.
       A pattern-list is a list of one or more patterns separated from each
       other with a & or .  A & signifies that all patterns must be matched
       whereas requires that only one pattern be matched.  Composite patterns
       can be formed with one or more of the following sub-patterns:
              ?(pattern-list)
                     Optionally matches any one of the given patterns.
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns.
              +(pattern-list)
                     Matches one or more occurrences of the given patterns.
              {n}(pattern-list)
                     Matches n occurrences of the given patterns.
              {m,n}(pattern-list)
                     Matches from m to n occurrences of the given patterns.  If
                     m is omitted, 0 will be used.  If n is omitted at least m
                     occurrences will be matched.
              @(pattern-list)
                     Matches exactly one of the given patterns.
              !(pattern-list)
                     Matches anything except one of the given patterns.
       By default, each pattern, or sub-pattern will match the longest string
       possible consistent with generating the longest overall match.  If more
       than one match is possible, the one starting closest to the beginning of
       the string will be chosen.   However, for each of the above compound
       patterns a - can be inserted in front of the ( to cause the shortest
       match to the specified pattern-list to be used.

       When pattern-list is contained within parentheses, the backslash
       character \ is treated specially even when inside a character class.
       All ANSI-C character escapes are recognized and match the specified
       character.  In addition the following escape sequences are recognized:
              \d     Matches any character in the digit class.
              \D     Matches any character not in the digit class.
              \s     Matches any character in the space class.
              \S     Matches any character not in the space class.
              \w     Matches any character in the word class.
              \W     Matches any character not in the word class.

       A pattern of the form %(pattern-pair(s)) is a sub-pattern that can be
       used to match nested character expressions.  Each pattern-pair is a two
       character sequence which cannot contain & or .  The first pattern-pair
       specifies the starting and ending characters for the match.  Each
       subsequent pattern-pair represents the beginning and ending characters of
       a nested group that will be skipped over when counting starting and
       ending character matches.  The behavior is unspecified when the first
       character of a pattern-pair is alpha-numeric except for the following:
              D      Causes the ending character to terminate the search for
                     this pattern without finding a match.
              E      Causes the ending character to be interpreted as an escape
                     character.
              L      Causes the ending character to be interpreted as a quote
                     character causing all characters to be ignored when looking
                     for a match.
              Q      Causes the ending character to be interpreted as a quote
                     character causing all characters other than any escape
                     character to be ignored when looking for a match.
       Thus, %({}Q"E\), matches characters starting at { until the matching } is
       found not counting any { or } that is inside a double quoted string or
       preceded by the escape character \.  Without the {} this pattern matches
       any C language string.

       Each sub-pattern in a composite pattern is numbered, starting at 1, by
       the location of the ( within the pattern.  The sequence \n, where n is a
       single digit and \n comes after the n-th. sub-pattern, matches the same
       string as the sub-pattern itself.

       Finally a pattern can contain sub-patterns of the form ∼(options:pattern-
       list), where either options or :pattern-list can be omitted.  Unlike the
       other compound patterns, these sub-patterns are not counted in the
       numbered sub-patterns.  :pattern-list must be omitted for options F, G, N
       , and V below.  If options is present, it can consist of one or more of
       the following:
              +      Enable the following options.  This is the default.
              -      Disable the following options.
              E      The remainder of the pattern uses extended regular
                     expression syntax like the egrep(1) command.
              F      The remainder of the pattern uses fgrep(1) expression
                     syntax.
              G      The remainder of the pattern uses basic regular expression
                     syntax like the grep(1) command.
              K      The remainder of the pattern uses shell pattern syntax.
                     This is the default.
              N      This is ignored.  However, when it is the first letter and
                     is used with file name generation, and no matches occur,
                     the file pattern expands to the empty string.
              X      The remainder of the pattern uses augmented regular
                     expression syntax like the xgrep(1) command.
              P      The remainder of the pattern uses perl(1) regular
                     expression syntax.  Not all perl regular expression syntax
                     is currently implemented.
              V      The remainder of the pattern uses System V regular
                     expression syntax.
              i      Treat the match as case insensitive.
              g      File the longest match (greedy).  This is the default.
              l      Left anchor the pattern.  This is the default for K style
                     patterns.
              r      Right anchor the pattern.  This is the default for K style
                     patterns.
       If both options and :pattern-list are specified, then the options apply
       only to  pattern-list.  Otherwise, these options remain in effect until
       they are disabled by a subsequent ∼(...) or at the end of the sub-pattern
       containing ∼(...).

   Quoting.
       Each of the metacharacters listed earlier (see Definitions above) has a
       special meaning to the shell and causes termination of a word unless
       quoted.  A character may be quoted (i.e., made to stand for itself) by
       preceding it with a \.  The pair \new-line is removed.  All characters
       enclosed between a pair of single quote marks (′′) that is not preceded
       by a $ are quoted.  A single quote cannot appear within the single
       quotes.  A single quoted string preceded by an unquoted $ is processed as
       an ANSI-C string except for the following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
              Expands to the collating element name.

       Inside double quote marks (""), parameter and command substitution occur
       and \ quotes the characters \, `, ", and $.  A $ in front of a double
       quoted string will be ignored in the "C" or "POSIX" locale, and may cause
       the string to be replaced by a locale specific string otherwise.  The
       meaning of $* and $@ is identical when not quoted or when used as a
       variable assignment value or as a file name.  However, when used as a
       command argument, "$*" is equivalent to "$1d$2d...", where d is the first
       character of the IFS variable, whereas "$@" is equivalent to "$1" "$2"
       ....  Inside grave quote marks (``), \ quotes the characters \, `, and $.
       If the grave quotes occur within double quotes, then \ also quotes the
       character ".

       The special meaning of reserved words or aliases can be removed by
       quoting any character of the reserved word.  The recognition of function
       names or built-in command names listed below cannot be altered by quoting
       them.

   Arithmetic Evaluation.
       The shell performs arithmetic evaluation for arithmetic substitution, to
       evaluate an arithmetic command, to evaluate an indexed array subscript,
       and to evaluate arguments to the built-in commands shift and let.
       Evaluations are performed using double precision floating point
       arithmetic or long double precision floating point for systems that
       provide this data type.  Floating point constants follow the ANSI-C
       programming language floating point conventions.  The floating point
       constants Nan and Inf can be use to represent "not a number" and infinity
       respectively.  Integer constants follow the ANSI-C programming language
       integer constant conventions although only single byte character
       constants are recognized and character casts are not recognized.  In
       addition constants can be of the form [base#]n where base is a decimal
       number between two and sixty-four representing the arithmetic base and n
       is a number in that base.  The digits above 9 are represented by the
       lower case letters, the upper case letters, @, and _ respectively.  For
       bases less than or equal to 36, upper and lower case characters can be
       used interchangeably.

       An arithmetic expression uses the same syntax, precedence, and
       associativity of expression as the C language.  All the C language
       operators that apply to floating point quantities can be used.  In
       addition, the operator ** can be used for exponentiation.  It has higher
       precedence than multiplication and is left associative.  In addition,
       when the value of an arithmetic variable or sub-expression can be
       represented as a long integer, all C language integer arithmetic
       operations can be performed.  Variables can be referenced by name within
       an arithmetic expression without using the parameter expansion syntax.
       When a variable is referenced, its value is evaluated as an arithmetic
       expression.

       Any of the following math library functions that are in the C math
       library can be used within an arithmetic expression:

       abs acos acosh asin asinh atan atan2 atanh cbrt ceil copysign cos cosh
       erf erfc exp exp2 expm1 fabs fdim finite floor fma fmax fmin fmod hypot
       ilogb int isfinite sinf isnan isnormal issubnormal issubordered iszero j0
       j1 jn lgamma log log10 log2 logb nearbyint pow remainder rint round scanb
       signbit sin sinh sqrt tan tanh tgamma trunc y0 y1 yn In addition,
       arithmetic functions can be defined as shell functions with a variant of
       the function name syntax,

       function .sh.math.name ident ... { list ;}
              where name is the function name used in the arithmetic expression.
              If the calling argument corresponding to ident is the name of an
              array variable, then ident is a name reference to this array.
              Otherwise, ident is a reference to long double precision floating
              point variable containing the value from the caller.  The value of
              .sh.value when the function returns is the value of this function.
              User defined functions can take up to 3 arguments and override C
              math library functions.

       An internal representation of a variable as a double precision floating
       point can be specified with the -E [n], -F [n], or -X [n] option of the
       typeset special built-in command.  The -E option causes the expansion of
       the value to be represented using scientific notation when it is
       expanded.  The optional option argument n defines the number of
       significant figures.  The -F option causes the expansion to be
       represented as a floating decimal number when it is expanded.  The -X
       option cause the expansion to be represented using the %a format defined
       by ISO C-99.  The optional option argument n defines the number of places
       after the decimal (or radix) point in this case.

       An internal integer representation of a variable can be specified with
       the -i [n] option of the typeset special built-in command.  The optional
       option argument n specifies an arithmetic base to be used when expanding
       the variable.  If you do not specify an arithmetic base, base 10 will be
       used.

       Arithmetic evaluation is performed on the value of each assignment to a
       variable with the -E, -F, -X, or -i attribute.  Assigning a floating
       point number to a variable whose type is an integer causes the fractional
       part to be truncated.

       Inside an arithmetic expression, all integer and floating point variables
       can be following by .MIN, .MAX, or .DIG to give the maximum value,
       mininum value, or number of significant digits for variables of that
       type.

       Floating point variables can be also followed by .INT_MAX or .INT_MIN to
       give the largest or smallest integers represented by that type.

       Floating point variables can also be followed by .EPSILON to give the
       distance to the next floating point number of that type.  Floating point
       variables can be followed by MAX_10_EXP to give the maximum base 10
       exponent that can be represented by that type.

       Inside an arithmetic expression, the following constants are recongnized
       and are of type typeset-lE.
              NaN    Not a number.  It is case insensitive.
              Inf    Infinity.  It is case insensitive.
              E
              PI
              1_PI   1.0/PI.
              2_PI   2.0/PI.
              PI_2   PI/2.0
              PI_4   PI/4.0.
              SQRTPI sqrt(PI).
              SQRT2  sqrt(2.0).
              SQRT1_2
                     sqrt(1./2.)
              LOGE   log(E)
              LOG10E log10(E)
              LN2    log(2.0)
              LOG2E  log2(E)

   Array Sorting.
       The -s option of the set built-in command can be used to sort its
       arguments or to sort indexed arrays, indexed arrays of compound
       variables, and indexed arrays of types (see "Type Variables" section
       below).  By default the sort order is defined by the current locale.  For
       compound variables and for types, the -K option for set can be followed
       by a comma separated list of sub-fields to sort on.  Each field can be
       followed by a : and the letter n for numerical sorting and/or r for
       reverse sorting.  For an plain indexed array the -K option can be
       followed by :n and  :r for numerical or reverse sorting.

   Prompting.
       When used interactively, the shell prompts with the value of PS1 after
       expanding it for parameter expansion, command substitution, and
       arithmetic substitution, before reading a command.  In addition, each
       single !  in the prompt is replaced by the command number.  A !!  is
       required to place !  in the prompt.  If at any time a new-line is typed
       and further input is needed to complete a command, then the secondary
       prompt (i.e., the value of PS2) is issued.

   Conditional Expressions.
       A conditional expression is used with the [[ compound command to test
       attributes of files and to compare strings.  Field splitting and file
       name generation are not performed on the words between [[ and ]].  Each
       expression can be constructed from one or more of the following unary or
       binary expressions:
       string True, if string is not null.
       -a file
              Same as -e below.  This is obsolete.
       -b file
              True, if file exists and is a block special file.
       -c file
              True, if file exists and is a character special file.
       -d file
              True, if file exists and is a directory.
       -e file
              True, if file exists.
       -f file
              True, if file exists and is an ordinary file.
       -g file
              True, if file exists and it has its setgid bit set.
       -k file
              True, if file exists and it has its sticky bit set.
       -n string
              True, if length of string is non-zero.
       -o ?option
              True, if option named option is a valid option name.
       -o option
              True, if option named option is on.
       -p file
              True, if file exists and is a fifo special file or a pipe.
       -r file
              True, if file exists and is readable by current process.
       -s file
              True, if file exists and has size greater than zero.
       -t fildes
              True, if file descriptor number fildes is open and associated with
              a terminal device.
       -u file
              True, if file exists and it has its setuid bit set.
       -v name
              True, if variable name is a valid variable name and is set.
       -w file
              True, if file exists and is writable by current process.
       -x file
              True, if file exists and is executable by current process.  If
              file exists and is a directory, then true if the current process
              has permission to search in the directory.
       -z string
              True, if length of string is zero.
       -L file
              True, if file exists and is a symbolic link.
       -h file
              True, if file exists and is a symbolic link.
       -N file
              True, if file exists and the modification time is greater than the
              last access time.
       -O file
              True, if file exists and is owned by the effective user id of this
              process.
       -G file
              True, if file exists and its group matches the effective group id
              of this process.
       -R name
              True if variable name is a name reference.
       -S file
              True, if file exists and is a socket.
       file1 -nt file2
              True, if file1 exists and file2 does not, or file1 is newer than
              file2.
       file1 -ot file2
              True, if file2 exists and file1 does not, or file1 is older than
              file2.
       file1 -ef file2
              True, if file1 and file2 exist and refer to the same file.
       string == pattern
              True, if string matches pattern.  Any part of pattern can be
              quoted to cause it to be matched as a string.  With a successful
              match to a pattern, the .sh.match array variable will contain the
              match and sub-pattern matches.
       string = pattern
              Same as == above, but is obsolete.
       string != pattern
              True, if string does not match pattern.  When the string matches
              the pattern the .sh.match array variable will contain the match
              and sub-pattern matches.
       string =∼ ere
              True if string matches the pattern ∼(E)ere where ere is an
              extended regular expression.
       string1 < string2
              True, if string1 comes before string2 based on the current locale.
       string1 > string2
              True, if string1 comes after string2 based on the current locale.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
              True, if exp1 is equal to exp2.
       exp1 -ne exp2
              True, if exp1 is not equal to exp2.
       exp1 -lt exp2
              True, if exp1 is less than exp2.
       exp1 -gt exp2
              True, if exp1 is greater than exp2.
       exp1 -le exp2
              True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
              True, if exp1 is greater than or equal to exp2.

       In each of the above expressions, if file is of the form /dev/fd/n, where
       n is an integer, then the test is applied to the open file whose
       descriptor number is n.

       A compound expression can be constructed from these primitives by using
       any of the following, listed in decreasing order of precedence.
       (expression)
              True, if expression is true.  Used to group expressions.
       ! expression
              True if expression is false.
       expression1 && expression2
              True, if expression1 and expression2 are both true.
       expression1 ⎪⎪ expression2
              True, if either expression1 or expression2 is true.

   Input/Output.
       Before a command is executed, its input and output may be redirected
       using a special notation interpreted by the shell.  The following may
       appear anywhere in a simple-command or may precede or follow a command
       and are not passed on to the invoked command.  Command substitution,
       parameter expansion, and arithmetic substitution occur before word or
       digit is used except as noted below.  File name generation occurs only if
       the shell is interactive and the pattern matches a single file.  Field
       splitting is not performed.

       In each of the following redirections, if file is of the form
       /dev/sctp/host/port, /dev/tcp/host/port, or /dev/udp/host/port, where
       host is a hostname or host address, and port is a service given by name
       or an integer port number, then the redirection attempts to make a tcp,
       sctp or udp connection to the corresponding socket.

       No intervening space is allowed between the characters of redirection
       operators.

       <word         Use file word as standard input (file descriptor 0).

       >word         Use file word as standard output (file descriptor 1).  If
                     the file does not exist then it is created.  If the file
                     exists, and the noclobber option is on, this causes an
                     error; otherwise, it is truncated to zero length.

       >|word        Same as >, except that it overrides the noclobber option.

       >;word        Write output to a temporary file.  If the command completes
                     successfully rename it to word, otherwise, delete the
                     temporary file.  >;word cannot be used with the exec(2).
                     built-in.

       >>word        Use file word as standard output.  If the file exists, then
                     output is appended to it (by first seeking to the end-of-
                     file); otherwise, the file is created.

       <>word        Open file word for reading and writing as standard input.

       <>;word       The same as <>word except that if the command completes
                     successfully, word is truncated to the offset at command
                     completion.  <>;word cannot be used with the exec(2).
                     built-in.

       <<[-]word     The shell input is read up to a line that is the same as
                     word after any quoting has been removed, or to an end-of-
                     file.  No parameter substitution, command substitution,
                     arithmetic substitution or file name generation is
                     performed on word.  The resulting document, called a here-
                     document, becomes the standard input.  If any character of
                     word is quoted, then no interpretation is placed upon the
                     characters of the document; otherwise, parameter expansion,
                     command substitution, and arithmetic substitution occur,
                     \new-line is ignored, and \ must be used to quote the
                     characters \, $, `.  If - is appended to <<, then all
                     leading tabs are stripped from word and from the document.
                     If # is appended to <<, then leading spaces and tabs will
                     be stripped off the first line of the document and up to an
                     equivalent indentation will be stripped from the remaining
                     lines and from word.  A tab stop is assumed to occur at
                     every 8 columns for the purposes of determining the
                     indentation.

       <<<word       A short form of here document in which word becomes the
                     contents of the here-document after any parameter
                     expansion, command substitution, and arithmetic
                     substitution occur.

       <&digit       The standard input is duplicated from file descriptor digit
                     (see dup(2)).  Similarly for the standard output using
                     >&digit.

       <&digit-      The file descriptor given by digit is moved to standard
                     input.  Similarly for the standard output using >&digit-.

       <&-           The standard input is closed.  Similarly for the standard
                     output using >&-.

       <&p           The input from the co-process is moved to standard input.

       >&p           The output to the co-process is moved to standard output.

       <#((expr))    Evaluate arithmetic expression expr and position file
                     descriptor 0 to the resulting value bytes from the start of
                     the file.  The variables CUR and EOF evaluate to the
                     current offset and end-of-file offset respectively when
                     evaluating expr.

       >#((offset))  The same as <# except applies to file descriptor 1.

       <#pattern     Seeks forward to the beginning of the next line containing
                     pattern.

       <##pattern    The same as <# except that the portion of the file that is
                     skipped is copied to standard output.

       If one of the above is preceded by a digit, with no intervening space,
       then the file descriptor number referred to is that specified by the
       digit (instead of the default 0 or 1).  If one of the above, other than
       >&- and the ># and <# forms, is preceded by {varname} with no intervening
       space, then a file descriptor number > 10 will be selected by the shell
       and stored in the variable varname.  If >&- or the any of the ># and <#
       forms is preceded by {varname} the value of varname defines the file
       descriptor to close or position.  For example:

              ... 2>&1

       means file descriptor 2 is to be opened for writing as a duplicate of
       file descriptor 1 and

              exec {n}<file

       means open file named file for reading and store the file descriptor
       number in variable n.

       The order in which redirections are specified is significant.  The shell
       evaluates each redirection in terms of the (file descriptor, file)
       association at the time of evaluation.  For example:

              ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates
       file descriptor 2 with the file associated with file descriptor 1 (i.e.
       fname).  If the order of redirections were reversed, file descriptor 2
       would be associated with the terminal (assuming file descriptor 1 had
       been) and then file descriptor 1 would be associated with file fname.

       If a command is followed by & and job control is not active, then the
       default standard input for the command is the empty file /dev/null.
       Otherwise, the environment for the execution of a command contains the
       file descriptors of the invoking shell as modified by input/output
       specifications.

   Environment.
       The environment (see environ(7)) is a list of name-value pairs that is
       passed to an executed program in the same way as a normal argument list.
       The names must be identifiers and the values are character strings.  The
       shell interacts with the environment in several ways.  On invocation, the
       shell scans the environment and creates a variable for each name found,
       giving it the corresponding value and attributes and marking it export.
       Executed commands inherit the environment.  If the user modifies the
       values of these variables or creates new ones, using the export or
       typeset -x commands, they become part of the environment.  The
       environment seen by any executed command is thus composed of any name-
       value pairs originally inherited by the shell, whose values may be
       modified by the current shell, plus any additions which must be noted in
       export or typeset -x commands.

       The environment for any simple-command or function may be augmented by
       prefixing it with one or more variable assignments.  A variable
       assignment argument is a word of the form identifier=value.  Thus:

              TERM=450 cmd args                  and
              (export TERM; TERM=450; cmd args)

       are equivalent (as far as the above execution of cmd is concerned except
       for special built-in commands listed below - those that are preceded with
       a dagger).

       If the obsolete -k option is set, all variable assignment arguments are
       placed in the environment, even if they occur after the command name.
       The following first prints a=b c and then c:

              echo a=b c
              set -k
              echo a=b c
       This feature is intended for use with scripts written for early versions
       of the shell and its use in new scripts is strongly discouraged.  It is
       likely to disappear someday.

   Functions.
       For historical reasons, there are two ways to define functions, the
       name() syntax and the function name syntax, described in the Commands
       section above.  Shell functions are read in and stored internally.  Alias
       names are resolved when the function is read.  Functions are executed
       like commands with the arguments passed as positional parameters.  (See
       Execution below.)

       Functions defined by the function name syntax and called by name execute
       in the same process as the caller and share all files and present working
       directory with the caller.  Traps caught by the caller are reset to their
       default action inside the function.  A trap condition that is not caught
       or ignored by the function causes the function to terminate and the
       condition to be passed on to the caller.  A trap on EXIT set inside a
       function is executed in the environment of the caller after the function
       completes.  Ordinarily, variables are shared between the calling program
       and the function.  However, the typeset special built-in command used
       within a function defines local variables whose scope includes the
       current function.  They can be passed to functions that they call in the
       variable assignment list that precedes the call or as arguments passed as
       name references.  Errors within functions return control to the caller.

       Functions defined with the name() syntax and functions defined with the
       function name syntax that are invoked with the .  special built-in are
       executed in the caller's environment and share all variables and traps
       with the caller.  Errors within these function executions cause the
       script that contains them to abort.

       The special built-in command return is used to return from function
       calls.

       Function names can be listed with the -f or +f option of the typeset
       special built-in command.  The text of functions, when available, will
       also be listed with -f.  Functions can be undefined with the -f option of
       the unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell script.
       Functions that need to be defined across separate invocations of the
       shell should be placed in a directory and the FPATH variable should
       contain the name of this directory.  They may also be specified in the
       ENV file.

   Discipline Functions.
       Each variable can have zero or more discipline functions associated with
       it.  The shell initially understands the discipline names get, set,
       append, and unset but can be added when defining new types.  On most
       systems others can be added at run time via the C programming interface
       extension provided by the builtin built-in utility.  If the get
       discipline is defined for a variable, it is invoked whenever the given
       variable is referenced.  If the variable .sh.value is assigned a value
       inside the discipline function, the referenced variable will evaluate to
       this value instead.  If the set discipline is defined for a variable, it
       is invoked whenever the given variable is assigned a value.  If the
       append discipline is defined for a variable, it is invoked whenever a
       value is appended to the given variable.  The variable .sh.value is given
       the value of the variable before invoking the discipline, and the
       variable will be assigned the value of .sh.value after the discipline
       completes.  If .sh.value is unset inside the discipline, then that value
       is unchanged.  If the unset discipline is defined for a variable, it is
       invoked whenever the given variable is unset.  The variable will not be
       unset unless it is unset explicitly from within this discipline function.

       The variable .sh.name contains the name of the variable for which the
       discipline function is called, .sh.subscript is the subscript of the
       variable, and .sh.value will contain the value being assigned inside the
       set discipline function.  The variable _ is a reference to the variable
       including the subscript if any.  For the set discipline, changing
       .sh.value will change the value that gets assigned.  Finally, the
       expansion ${var.name}, when name is the name of a discipline, and there
       is no variable of this name, is equivalent to the command substitution ${
       var.name;}.


   Name Spaces.
       Commands and functions that are executed as part of the list of a
       namespace command that modify variables or create new ones, create a new
       variable whose name is the name of the name space as given by identifier
       preceded by ..  When a variable whose name is name is referenced, it is
       first searched for using .identifier.name.  Similarly, a function defined
       by a command in the namespace list is created using the name space name
       preceded by a ..

       When  the list of a namespace command contains a namespace command, the
       names of variables and functions that are created consist of the variable
       or function name preceded by the list of identifiers each preceded by ..

       Outside of a name space, a variable or function created inside a name
       space can be referenced by preceding it with the name space name.

       By default, variables staring with .sh are in the sh name space.


   Type Variables.
       Typed variables provide a way to create data structure and objects.  A
       type can be defined either by a shared library, by the enum built-in
       command described below, or by using the new -T option of the typeset
       built-in command.  With the -T option of typeset, the type name,
       specified as an option argument to -T, is set with a compound variable
       assignment that defines the type.  Function definitions can appear inside
       the compound variable assignment and these become discipline functions
       for this type and can be invoked or redefined by each instance of the
       type.  The function name create is treated specially.  It is invoked for
       each instance of the type that is created but is not inherited and cannot
       be redefined for each instance.

       When a type is defined a special built-in command of that name is added.
       These built-ins are declaration commands and follow the same expansion
       rules as all the special built-in commands defined below that are
       preceded by ††.  These commands can subsequently be used inside further
       type definitions.  The man page for these commands can be generated by
       using the --man option or any of the other -- options described with
       getopts.  The -r, -a, -A, -h, and -S options of typeset are permitted
       with each of these new built-ins.

       An instance of a type is created by invoking the type name followed by
       one or more instance names.  Each instance of the type is initialized
       with a copy of the sub-variables except for sub-variables that are
       defined with the -S option.  Variables defined with the -S are shared by
       all instances of the type.  Each instance can change the value of any
       sub-variable and can also define new discipline functions of the same
       names as those defined by the type definition as well as any standard
       discipline names.  No additional sub-variables can be defined for any
       instance.

       When defining a type, if the value of a sub-variable is not set and the
       -r attribute is specified, it causes the sub-variable to be a required
       sub-variable.  Whenever an instance of a type is created, all required
       sub-variables must be specified.  These sub-variables become readonly in
       each instance.

       When unset is invoked on a sub-variable within a type, and the -r
       attribute has not been specified for this field, the value is reset to
       the default value associative with the type.  Invoking unset on a type
       instance not contained within another type deletes all sub-variables and
       the variable itself.

       A type definition can be derived from another type definition by defining
       the first sub-variable name as _ and defining its type as the base type.
       Any remaining definitions will be additions and modifications that apply
       to the new type.  If the new type name is the same as that of the base
       type, the type will be replaced and the original type will no longer be
       accessible.

       The typeset command with the -T and no option argument or operands will
       write all the type definitions to standard output in a form that can be
       read in to create all the types.

   Jobs.
       If the monitor option of the set command is turned on, an interactive
       shell associates a job with each pipeline.  It keeps a table of current
       jobs, printed by the jobs command, and assigns them small integer
       numbers.  When a job is started asynchronously with &, the shell prints a
       line which looks like:

            [1] 1234

       indicating that the job which was started asynchronously was job number 1
       and had one (top-level) process, whose process id was 1234.

       This paragraph and the next require features that are not in all versions
       of UNIX and may not apply.  If you are running a job and wish to do
       something else you may hit the key ^Z (control-Z) which sends a STOP
       signal to the current job.  The shell will then normally indicate that
       the job has been `Stopped', and print another prompt.  You can then
       manipulate the state of this job, putting it in the background with the
       bg command, or run some other commands and then eventually bring the job
       back into the foreground with the foreground command fg.  A ^Z takes
       effect immediately and is like an interrupt in that pending output and
       unread input are discarded when it is typed.

       A job being run in the background will stop if it tries to read from the
       terminal.  Background jobs are normally allowed to produce output, but
       this can be disabled by giving the command stty tostop.  If you set this
       tty option, then background jobs will stop when they try to produce
       output like they do when they try to read input.

       A job pool is a collection of jobs started with list & associated with a
       name.

       There are several ways to refer to jobs in the shell.  A job can be
       referred to by the process id of any process of the job or by one of the
       following:
       %number
              The job with the given number.
       pool   All the jobs in the job pool named by pool.
       pool.number
              The job number number in the job pool named by pool.
       %string
              Any job whose command line begins with string.
       %?string
              Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous job.  In addition, unless noted otherwise, wherever a job
              can be specified, the name of a background job pool can be used to
              represent all the jobs in that pool.

       The shell learns immediately whenever a process changes state.  It
       normally informs you whenever a job becomes blocked so that no further
       progress is possible, but only just before it prints a prompt.  This is
       done so that it does not otherwise disturb your work.  The notify option
       of the set command causes the shell to print these job change messages as
       soon as they occur.

       When the monitor option is on, each background job that completes
       triggers any trap set for CHLD.

       When you try to leave the shell while jobs are running or stopped, you
       will be warned that `You have stopped(running) jobs.'  You may use the
       jobs command to see what they are.  If you immediately try to exit again,
       the shell will not warn you a second time, and the stopped jobs will be
       terminated.  When a login shell receives a HUP signal, it sends a HUP
       signal to each job that has not been disowned with the disown built-in
       command described below.

   Signals.
       The INT and QUIT signals for an invoked command are ignored if the
       command is followed by & and the monitor option is active.  Otherwise,
       signals have the values inherited by the shell from its parent (but see
       also the trap built-in command below).

   Execution.
       Each time a command is read, the above substitutions are carried out.  If
       the command name matches one of the Special Built-in Commands listed
       below, it is executed within the current shell process.  Next, the
       command name is checked to see if it matches a user defined function.  If
       it does, the positional parameters are saved and then reset to the
       arguments of the function call.  A function is also executed in the
       current shell process.  When the function completes or issues a return,
       the positional parameter list is restored.  For functions defined with
       the function name syntax, any trap set on EXIT within the function is
       executed.  The exit value of a function is the value of the last command
       executed.  If a command name is not a special built-in command or a user
       defined function, but it is one of the built-in commands listed below, it
       is executed in the current shell process.

       The shell variables PATH followed by the variable FPATH defines the list
       of directories to search for the command name.  Alternative directory
       names are separated by a colon (:).  The default path is equal to
       getconf PATH output.  The current directory can be specified by two or
       more adjacent colons, or by a colon at the beginning or end of the path
       list.  If the command name contains a /, then the search path is not
       used.  Otherwise, each directory in the list of directories defined by
       PATH and FPATH is checked in order.  If the directory being searched is
       contained in FPATH and contains a file whose name matches the command
       being searched, then this file is loaded into the current shell
       environment as if it were the argument to the . command except that only
       preset aliases are expanded, and a function of the given name is executed
       as described above.

       If this directory is not in FPATH the shell first determines whether
       there is a built-in version of a command corresponding to a given
       pathname and if so it is invoked in the current process.  If no built-in
       is found, the shell checks for a file named .paths in this directory.  If
       found and there is a line of the form FPATH=path where path names an
       existing directory then that directory is searched immediately after the
       current directory as if it were found in the FPATH variable.  If path
       does not begin with /, it is checked for relative to the directory being
       searched.

       The .paths file is then checked  for a line of the form
       PLUGIN_LIB=libname [ : libname ] ... .  Each library named by libname
       will be searched for as if it were an option argument to builtin -f, and
       if it contains a built-in of the specified name this will be executed
       instead of a command by this name.  Any built-in loaded from a library
       found this way will be associated with the directory containing the
       .paths file so it will only execute if not found in an earlier directory.

       Finally, the directory will be checked for a file of the given name.  If
       the file has execute permission but is not an a.out file, it is assumed
       to be a file containing shell commands.  A separate shell is spawned to
       read it.  All non-exported variables are removed in this case.  If the
       shell command file doesn't have read permission, or if the setuid and/or
       setgid bits are set on the file, then the shell executes an agent whose
       job it is to set up the permissions and execute the shell with the shell
       command file passed down as an open file.  If the .paths contains a line
       of the form name=value in the first or second line, then the environment
       variable name is modified by prepending the directory specified by value
       to the directory list.  If value is not an absolute directory, then it
       specifies a directory relative to the directory that the executable was
       found.  If the environment variable name does not already exist it will
       be added to the environment list for the specified command.  A
       parenthesized command is executed in a sub-shell without removing non-
       exported variables.

   Command Re-entry.
       The text of the last HISTSIZE (default 512) commands entered from a
       terminal device is saved in a history file.  The file $HOME/.sh_history
       is used if the HISTFILE variable is not set or if the file it names is
       not writable.  A shell can access the commands of all interactive shells
       which use the same named HISTFILE.  The built-in command hist is used to
       list or edit a portion of this file.  The portion of the file to be
       edited or listed can be selected by number or by giving the first
       character or characters of the command.  A single command or range of
       commands can be specified.  If you do not specify an editor program as an
       argument to hist then the value of the variable HISTEDIT is used.  If
       HISTEDIT is unset, the obsolete variable FCEDIT is used.  If FCEDIT is
       not defined, then /bin/ed is used.  The edited command(s) is printed and
       re-executed upon leaving the editor unless you quit without writing.  The
       -s option (and in obsolete versions, the editor name -) is used to skip
       the editing phase and to re-execute the command.  In this case a
       substitution parameter of the form old=new can be used to modify the
       command before execution.  For example, with the preset alias r, which is
       aliased to ′hist -s′, typing `r bad=good c' will re-execute the most
       recent command which starts with the letter c, replacing the first
       occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally, each command line entered from a terminal device is simply
       typed followed by a new-line (`RETURN' or `LINE FEED').  If either the
       emacs, gmacs, or vi option is active, the user can edit the command line.
       To be in either of these edit modes set the corresponding option.  An
       editing option is automatically selected each time the VISUAL or EDITOR
       variable is assigned a value ending in either of these option names.

       The editing features require that the user's terminal accept `RETURN' as
       carriage return without line feed and that a space (` ') must overwrite
       the current character on the screen.

       Unless the multiline option is on, the editing modes implement a concept
       where the user is looking through a window at the current line.  The
       window width is the value of COLUMNS if it is defined, otherwise 80.  If
       the window width is too small to display the prompt and leave at least 8
       columns to enter input, the prompt is truncated from the left.  If the
       line is longer than the window width minus two, a mark is displayed at
       the end of the window to notify the user.  As the cursor moves and
       reaches the window boundaries the window will be centered about the
       cursor.  The mark is a > (<, *) if the line extends on the right (left,
       both) side(s) of the window.

       The search commands in each edit mode provide access to the history file.
       Only strings are matched, not patterns, although a leading ^ in the
       string restricts the match to begin at the first character in the line.

       Each of the edit modes has an operation to list the files or commands
       that match a partially entered word.  When applied to the first word on
       the line, or the first word after a ;, , &, or (, and the word does not
       begin with or contain a /, the list of aliases, functions, and
       executable commands defined by the PATH variable that could match the
       partial word is displayed.  Otherwise, the list of files that match the
       given word is displayed.  If the partially entered word does not contain
       any file expansion characters, a * is appended before generating these
       lists.  After displaying the generated list, the input line is redrawn.
       These operations are called command name listing and file name listing,
       respectively.  There are additional operations, referred to as command
       name completion and file name completion, which compute the list of
       matching commands or files, but instead of printing the list, replace the
       current word with a complete or partial match.  For file name completion,
       if the match is unique, a / is appended if the file is a directory and a
       space is appended if the file is not a directory.  Otherwise, the longest
       common prefix for all the matching files replaces the word.  For command
       name completion, only the portion of the file names after the last / are
       used to find the longest command prefix.  If only a single name matches
       this prefix, then the word is replaced with the command name followed by
       a space.  When using a tab for completion that does not yield a unique
       match, a subsequent tab will provide a numbered list of matching
       alternatives.  A specific selection can be made by entering the selection
       number followed by a tab.

   Key Bindings.
       The KEYBD trap can be used to intercept keys as they are typed and change
       the characters that are actually seen by the shell.  This trap is
       executed after each character (or sequence of characters when the first
       character is ESC) is entered while reading from a terminal.  The variable
       .sh.edchar contains the character or character sequence which generated
       the trap.  Changing the value of .sh.edchar in the trap action causes the
       shell to behave as if the new value were entered from the keyboard rather
       than the original value.

       The variable .sh.edcol is set to the input column number of the cursor at
       the time of the input.  The variable .sh.edmode is set to ESC when in vi
       insert mode (see below) and is null otherwise.  By prepending
       ${.sh.editmode} to a value assigned to .sh.edchar it will cause the shell
       to change to control mode if it is not already in this mode.

       This trap is not invoked for characters entered as arguments to editing
       directives, or while reading input for a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.  The
       only difference between these two modes is the way they handle ^T.  To
       edit, the user moves the cursor to the point needing correction and then
       inserts or deletes characters or words as needed.  All the editing
       commands are control characters or escape sequences.  The notation for
       control characters is caret (^) followed by the character.  For example,
       ^F is the notation for control F.  This is entered by depressing `f'
       while holding down the `CTRL' (control) key.  The `SHIFT' key is not
       depressed.  (The notation ^?  indicates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a character.  For
       example, M-f (pronounced Meta f) is entered by depressing ESC (ascii 033)
       followed by `f'.  (M-F would be the notation for ESC followed by `SHIFT'
       (capital) `F'.)

       All edit commands operate from any place on the line (not just at the
       beginning).  Neither the `RETURN' nor the `LINE FEED' key is entered
       after edit commands except when noted.

       ^F        Move cursor forward (right) one character.
       M-[C      Move cursor forward (right) one character.
       M-f       Move cursor forward one word.  (The emacs editor's idea of a
                 word is a string of characters consisting of only letters,
                 digits and underscores.)
       ^B        Move cursor backward (left) one character.
       M-[D      Move cursor backward (left) one character.
       M-b       Move cursor backward one word.
       ^A        Move cursor to start of line.
       M-[H      Move cursor to start of line.
       ^E        Move cursor to end of line.
       M-[Y      Move cursor to end of line.
       ^]char    Move cursor forward to character char on current line.
       M-^]char  Move cursor backward to character char on current line.
       ^X^X      Interchange the cursor and mark.
       erase     (User defined erase character as defined by the stty(1)
                 command, usually ^H or #.)  Delete previous character.
       lnext     (User defined literal next character as defined by the stty(1)
                 command, or ^V if not defined.)  Removes the next character's
                 editing features (if any).
       ^D        Delete current character.
       M-d       Delete current word.
       M-^H      (Meta-backspace) Delete previous word.
       M-h       Delete previous word.
       M-^?      (Meta-DEL) Delete previous word (if your interrupt character is
                 ^?  (DEL, the default) then this command will not work).
       ^T        Transpose current character with previous character and advance
                 the cursor in emacs mode.  Transpose two previous characters in
                 gmacs mode.
       ^C        Capitalize current character.
       M-c       Capitalize current word.
       M-l       Change the current word to lower case.
       ^K        Delete from the cursor to the end of the line.  If preceded by
                 a numerical parameter whose value is less than the current
                 cursor position, then delete from given position up to the
                 cursor.  If preceded by a numerical parameter whose value is
                 greater than the current cursor position, then delete from
                 cursor up to given cursor position.
       ^W        Kill from the cursor to the mark.
       M-p       Push the region from the cursor to the mark on the stack.
       kill      (User defined kill character as defined by the stty command,
                 usually ^G or @.)  Kill the entire current line.  If two kill
                 characters are entered in succession, all kill characters from
                 then on cause a line feed (useful when using paper terminals).
       ^Y        Restore last item removed from line. (Yank item back to the
                 line.)
       ^L        Line feed and print current line.
       M-^L      Clear the screen.
       ^@        (Null character) Set mark.
       M-space   (Meta space) Set mark.
       ^J        (New line) Execute the current line.
       ^M        (Return) Execute the current line.
       eof       End-of-file character, normally ^D, is processed as an End-of-
                 file only if the current line is null.
       ^P        Fetch previous command.  Each time ^P is entered the previous
                 command back in time is accessed.  Moves back one line when not
                 on the first line of a multi-line command.
       M-[A      If the cursor is at the end of the line, it is equivalent to ^R
                 with string set to the contents of the current line.
                 Otherwise, it is equivalent to ^P.
       M-<       Fetch the least recent (oldest) history line.
       M->       Fetch the most recent (youngest) history line.
       ^N        Fetch next command line.  Each time ^N is entered the next
                 command line forward in time is accessed.
       M-[B      Equivalent to ^N.
       ^Rstring  Reverse search history for a previous command line containing
                 string.  If a parameter of zero is given, the search is
                 forward.  String is terminated by a `RETURN' or `NEW LINE'.  If
                 string is preceded by a ^, the matched line must begin with
                 string.  If string is omitted, then the next command line
                 containing the most recent string is accessed.  In this case a
                 parameter of zero reverses the direction of the search.
       ^O        Operate - Execute the current line and fetch the next line
                 relative to current line from the history file.
       M-digits  (Escape) Define numeric parameter, the digits are taken as a
                 parameter to the next command.  The commands that accept a
                 parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
                 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter  Soft-key - Your alias list is searched for an alias by the name
                 _letter and if an alias of this name is defined, its value will
                 be inserted on the input queue.  The letter must not be one of
                 the above meta-functions.
       M-[letter Soft-key - Your alias list is searched for an alias by the name
                 __letter and if an alias of this name is defined, its value
                 will be inserted on the input queue.  This can be used to
                 program function keys on many terminals.
       M-.       The last word of the previous command is inserted on the line.
                 If preceded by a numeric parameter, the value of this parameter
                 determines which word to insert rather than the last word.
       M-_       Same as M-..
       M-*       Attempt file name generation on the current word.  An asterisk
                 is appended if the word doesn't match any file or contain any
                 special pattern characters.
       M-ESC     Command or file name completion as described above.
       ^I tab    Attempts command or file name completion as described above.
                 If a partial completion occurs, repeating this will behave as
                 if M-= were entered.  If no match is found or entered after
                 space, a tab is inserted.
       M-=       If not preceded by a numeric parameter, it generates the list
                 of matching commands or file names as described above.
                 Otherwise, the word under the cursor is replaced by the item
                 corresponding to the value of the numeric parameter from the
                 most recently generated command or file list.  If the cursor is
                 not on a word, it is inserted instead.
       ^U        Multiply parameter of next command by 4.
       \         Escape next character.  Editing characters, the user's erase,
                 kill and interrupt (normally ^?)  characters may be entered in
                 a command line or in a search string if preceded by a \.  The \
                 removes the next character's editing features (if any).
       M-^V      Display version of the shell.
       M-#       If the line does not begin with a #, a # is inserted at the
                 beginning of the line and after each new-line, and the line is
                 entered.  This causes a comment to be inserted in the history
                 file.  If the line begins with a #, the # is deleted and one #
                 after each new-line is also deleted.

   Vi Editing Mode.
       There are two typing modes.  Initially, when you enter a command you are
       in the input mode.  To edit, the user enters control mode by typing ESC
       (033) and moves the cursor to the point needing correction and then
       inserts or deletes characters or words as needed.  Most control commands
       accept an optional repeat count prior to the command.

       When in vi mode on most systems, canonical processing is initially
       enabled and the command will be echoed again if the speed is 1200 baud or
       greater and it contains any control characters or less than one second
       has elapsed since the prompt was printed.  The ESC character terminates
       canonical processing for the remainder of the command and the user can
       then modify the command line.  This scheme has the advantages of
       canonical processing with the type-ahead echoing of raw mode.

       If the option viraw is also set, the terminal will always have canonical
       processing disabled.  This mode is implicit for systems that do not
       support two alternate end of line delimiters, and may be helpful for
       certain terminals.

        Input Edit Commands
              By default the editor is in input mode.
              erase     (User defined erase character as defined by the stty
                        command, usually ^H or #.)  Delete previous character.
              ^W        Delete the previous blank separated word.
              eof       As the first character of the line causes the shell to
                        terminate unless the ignoreeof option is set.  Otherwise
                        this character is ignored.
              lnext     (User defined literal next character as defined by the
                        stty(1) or ^V if not defined.)  Removes the next
                        character's editing features (if any).
              \         Escape the next erase or kill character.
              ^I tab    Attempts command or file name completion as described
                        above and returns to input mode.  If a partial
                        completion occurs, repeating this will behave as if =
                        were entered from control mode.  If no match is found or
                        entered after space, a tab is inserted.
        Motion Edit Commands
              These commands will move the cursor.
              [count]l  Cursor forward (right) one character.
              [count][C Cursor forward (right) one character.
              [count]w  Cursor forward one alpha-numeric word.
              [count]W  Cursor to the beginning of the next word that follows a
                        blank.
              [count]e  Cursor to end of word.
              [count]E  Cursor to end of the current blank delimited word.
              [count]h  Cursor backward (left) one character.
              [count][D Cursor backward (left) one character.
              [count]b  Cursor backward one word.
              [count]B  Cursor to preceding blank separated word.
              [count]Cursor to column count.
              [count]fc Find the next character c in the current line.
              [count]Fc Find the previous character c in the current line.
              [count]tc Equivalent to f followed by h.
              [count]Tc Equivalent to F followed by l.
              [count];  Repeats count times, the last single character find
                        command, f, F, t, or T.
              [count],  Reverses the last single character find command count
                        times.
              0         Cursor to start of line.
              ^         Cursor to start of line.
              [H        Cursor to first non-blank character in line.
              $         Cursor to end of line.
              [Y        Cursor to end of line.
              %         Moves to balancing (, ), {, }, [, or ].  If cursor is
                        not on one of the above characters, the remainder of the
                        line is searched for the first occurrence of one of the
                        above characters first.
        Search Edit Commands
              These commands access your command history.
              [count]k  Fetch previous command.  Each time k is entered the
                        previous command back in time is accessed.
              [count]-  Equivalent to k.
              [count][A If cursor is at the end of the line it is equivalent to
                        / with string^set to the contents of the current line.
                        Otherwise, it is equivalent to k.
              [count]j  Fetch next command.  Each time j is entered the next
                        command forward in time is accessed.
              [count]+  Equivalent to j.
              [count][B Equivalent to j.
              [count]G  The command number count is fetched.  The default is the
                        least recent history command.
              /string   Search backward through history for a previous command
                        containing string.  String is terminated by a `RETURN'
                        or `NEW LINE'.  If string is preceded by a ^, the
                        matched line must begin with string.  If string is null,
                        the previous string will be used.
              ?string   Same as / except that search will be in the forward
                        direction.
              n         Search for next match of the last pattern to / or ?
                        commands.
              N         Search for next match of the last pattern to / or ?, but
                        in reverse direction.
        Text Modification Edit Commands
              These commands will modify the line.
              a         Enter input mode and enter text after the current
                        character.
              A         Append text to the end of the line.  Equivalent to $a.
              [count]cmotion
              c[count]motion
                        Delete current character through the character that
                        motion would move the cursor to and enter input mode.
                        If motion is c, the entire line will be deleted and
                        input mode entered.
              C         Delete the current character through the end of line and
                        enter input mode.  Equivalent to c$.
              S         Equivalent to cc.
              [count]s  Replace characters under the cursor in input mode.
              D         Delete the current character through the end of line.
                        Equivalent to d$.
              [count]dmotion
              d[count]motion
                        Delete current character through the character that
                        motion would move to.  If motion is d , the entire line
                        will be deleted.
              i         Enter input mode and insert text before the current
                        character.
              I         Insert text before the beginning of the line.
                        Equivalent to 0i.
              [count]P  Place the previous text modification before the cursor.
              [count]p  Place the previous text modification after the cursor.
              R         Enter input mode and replace characters on the screen
                        with characters you type overlay fashion.
              [count]rc Replace the count character(s) starting at the current
                        cursor position with c, and advance the cursor.
              [count]x  Delete current character.
              [count]X  Delete preceding character.
              [count].  Repeat the previous text modification command.
              [count]Invert the case of the count character(s) starting at
                        the current cursor position and advance the cursor.
              [count]_  Causes the count word of the previous command to be
                        appended and input mode entered.  The last word is used
                        if count is omitted.
              *         Causes an * to be appended to the current word and file
                        name generation attempted.  If no match is found, it
                        rings the bell.  Otherwise, the word is replaced by the
                        matching pattern and input mode is entered.
              \         Command or file name completion as described above.
        Other Edit Commands
              Miscellaneous commands.
              [count]ymotion
              y[count]motion
                        Yank current character through character that motion
                        would move the cursor to and puts them into the delete
                        buffer.  The text and cursor are unchanged.
              yy        Yanks the entire line.
              Y         Yanks from current position to end of line.  Equivalent
                        to y$.
              u         Undo the last text modifying command.
              U         Undo all the text modifying commands performed on the
                        line.
              [count]v  Returns the command hist -e ${VISUAL:-${EDITOR:-vi}}
                        count in the input buffer.  If count is omitted, then
                        the current line is used.
              ^L        Line feed and print current line.  Has effect only in
                        control mode.
              ^J        (New line) Execute the current line, regardless of mode.
              ^M        (Return) Execute the current line, regardless of mode.
              #         If the first character of the command is a #, then this
                        command deletes this # and each # that follows a
                        newline.  Otherwise, sends the line after inserting a #
                        in front of each line in the command.  Useful for
                        causing the current line to be inserted in the history
                        as a comment and uncommenting previously commented
                        commands in the history file.
              [count]=  If count is not specified, it generates the list of
                        matching commands or file names as described above.
                        Otherwise, the word under the cursor is replaced by the
                        count item from the most recently generated command or
                        file list.  If the cursor is not on a word, it is
                        inserted instead.
              @letter   Your alias list is searched for an alias by the name
                        _letter and if an alias of this name is defined, its
                        value will be inserted on the input queue for
                        processing.
              ^V        Display version of the shell.

   Programmable Completion.
       By default, hitting the tab key causes the current word to be matched
       against files starting with the characters you typed and adding as many
       characters that provide a unique match.  If the matching prefix is not
       unique hitting tab again will output a numbered list with the choices and
       entering number tab will replace the current word with that selection.

       Programmable completion allows you to control how words are expanded when
       you enter the tab key for one or more specified commands.  The complete
       built-in command allows you to specify how to complete the current word
       of the specified command.

   Built-in Commands.
       The following simple-commands are executed in the shell process.
       Input/Output redirection is permitted.  Unless otherwise indicated, the
       output is written on file descriptor 1 and the exit status, when there is
       no syntax error, is zero.  Except for :, true, false, echo, newgrp, and
       login, all built-in commands accept -- to indicate end of options.  They
       also interpret the option --man as a request to display the man page onto
       standard error and -?  as a help request which prints a usage message on
       standard error.  Commands that are preceded by one or two † symbols are
       special built-in commands and are treated specially in the following
       ways:
       1.     Variable assignment lists preceding the command remain in effect
              when the command completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words following a command preceded by †† that are in the format of
              a variable assignment are expanded with the same rules as a
              variable assignment.  This means that tilde substitution is
              performed after the = sign and field splitting and file name
              generation are not performed.  These are called declaration built-
              ins.

       † : [ arg ... ]
              The command only expands parameters.

       † . name [ arg ... ]
              If name is a function defined with the function name reserved word
              syntax, the function is executed in the current environment (as if
              it had been defined with the name() syntax.)  Otherwise if name
              refers to a file, the file is read in its entirety and the
              commands are executed in the current shell environment.  The
              search path specified by PATH is used to find the directory
              containing the file.  If any arguments arg are given, they become
              the positional parameters while processing the .  command and the
              original positional parameters are restored upon completion.
              Otherwise the positional parameters are unchanged.  The exit
              status is the exit status of the last command executed.

       †† alias [ -ptx ]  [ name[ =value  ] ] ...
              alias with no arguments prints the list of aliases in the form
              name=value on standard output.  The -p option causes the word
              alias to be inserted before each one.  When one or more arguments
              are given, an alias is defined for each name whose value is given.
              A trailing space in value causes the next word to be checked for
              alias substitution.  The obsolete -t option is used to set and
              list tracked aliases.  The value of a tracked alias is the full
              pathname corresponding to the given name.  The value becomes
              undefined when the value of PATH is reset but the alias remains
              tracked.  Without the -t option, for each name in the argument
              list for which no value is given, the name and value of the alias
              is printed.  The obsolete -x option has no effect.  The exit
              status is non-zero if a name is given, but no value, and no alias
              has been defined for the name.

       bg [ job... ]
              This command is only on systems that support job control.  Puts
              each specified job into the background.  The current job is put in
              the background if job is not specified.  See Jobs for a
              description of the format of job.

       † break [ n ]
              Exit from the enclosing for, while, until, or select loop, if any.
              If n is specified, then break n levels.

       builtin [ -dsp ] [ -f file ] [ name ... ]
              If name is not specified, and no -f option is specified, the
              built-ins are printed on standard output.  The -s option prints
              only the special built-ins.  Otherwise, each name represents the
              pathname whose basename is the name of the built-in.  The entry
              point function name is determined by prepending b_ to the built-in
              name.  A built-in specified by a pathname will only be executed
              when that pathname would be found during the path search.  Built-
              ins found in libraries loaded via the .paths file will be
              associate with the pathname of the directory containing the .paths
              file.
              The ISO C/C++ prototype is b_mycommand(int argc, char *argv[],
              void *context) for the builtin command mycommand where argv is
              array an of argc elements and context is an optional pointer to a
              Shell_t structure as described in <ast/shell.h>.
              Special built-ins cannot be bound to a pathname or deleted.  The
              -d option deletes each of the given built-ins.  On systems that
              support dynamic loading, the -f option names a shared library
              containing the code for built-ins.  The shared library prefix
              and/or suffix, which depend on the system, can be omitted.  Once a
              library is loaded, its symbols become available for subsequent
              invocations of builtin.  Multiple libraries can be specified with
              separate invocations of the builtin command.  Libraries are
              searched in the reverse order in which they are specified.  When a
              library is loaded, it looks for a function in the library whose
              name is lib_init() and invokes this function with an argument of
              0.
              The -p causes the output to be in a form of builtin commands that
              can be used as input to the shell to recreate the current set of
              builtins.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
              This command can be in either of two forms.  In the first form it
              changes the current directory to arg.  If arg is - the directory
              is changed to the previous directory.  The shell variable HOME is
              the default arg.  The variable PWD is set to the current
              directory.  The shell variable CDPATH defines the search path for
              the directory containing arg.  Alternative directory names are
              separated by a colon (:).  The default path is <null> (specifying
              the current directory).  Note that the current directory is
              specified by a null path name, which can appear immediately after
              the equal sign or between the colon delimiters anywhere else in
              the path list.  If arg begins with a / then the search path is not
              used.  Otherwise, each directory in the path is searched for arg.
              The second form of cd substitutes the string new for the string
              old in the current directory name, PWD, and tries to change to
              this new directory.
              By default, symbolic link names are treated literally when finding
              the directory name.  This is equivalent to the -L option.  The -P
              option causes symbolic links to be resolved when determining the
              directory.  The last instance of -L or -P on the command line
              determines which method is used.
              The cd command may not be executed by rksh.

       command [ -pvxV ] name [ arg ... ]
              Without the -v or -V options, command executes name with the
              arguments given by arg.  The -p option causes a default path to be
              searched rather than the one defined by the value of PATH.
              Functions will not be searched for when finding name.  In
              addition, if name refers to a special built-in, none of the
              special properties associated with the leading daggers will be
              honored.  (For example, the predefined alias redirect=′command
              exec′ prevents a script from terminating when an invalid
              redirection is given.)  With the -x option, if command execution
              would result in a failure because there are too many arguments,
              errno E2BIG, the shell will invoke command name multiple times
              with a subset of the arguments on each invocation.  Arguments that
              occur prior to the first word that expands to multiple arguments
              and after the last word that expands to multiple arguments will be
              passed on each invocation.  The exit status will be the maximum
              invocation exit status.  With the -v option, command is equivalent
              to the built-in whence command described below.  The -V option
              causes command to act like whence -v.

       † continue [ n ]
              Resume the next iteration of the enclosing for, while, until, or
              select loop.  If n is specified, then resume at the n-th enclosing
              loop.

       disown [ job... ]
              Causes the shell not to send a HUP signal to each given job, or
              all active jobs if job is omitted, when a login shell terminates.

       echo [ -n  -e ] [  arg ... ]
              echo builtin prints all of its arguments separated by space and
              terminated by new-line.  -n will skip putting a newline character
              at the end of output. If -e is set, it will enable interpreting
              escape sequences.


       †† enum [ -i  ] type[=(value ...) ]
              Creates a declaration command named type that is an integer type
              that allows one of the specified values as enumeration names.  If
              =(value ...) is omitted, then type must be an indexed array
              variable with at least two elements and the values are taken from
              this array variable.  If -i is specified the values are case
              insensitive.
              When an enumeration variable is used in arithmetic expression, its
              value is the index into the array that defined it starting from
              index 0.  Enumeration strings can be used in an arithmetic
              expression when comparing against an enumeration variable.  Also,
              each non-subscripted enumeration variable followed by .name where
              name is one of the enumeration names expands to the index
              corresponding to name.
              The enum _Bool is created with values true and false.  The
              predefined alias bool is defined as _Bool.

       † eval [ arg ... ]
              The arguments are read as input to the shell and the resulting
              command(s) executed.

       † exec [ -c ] [ -a name ] [ arg ... ]
              If arg is given, the command specified by the arguments is
              executed in place of this shell without creating a new process.
              The -c option causes the environment to be cleared before applying
              variable assignments associated with the exec invocation.  The -a
              option causes name rather than the first arg, to become argv[0]
              for the new process.  Input/output arguments may appear and affect
              the current process.  If arg is not given, the effect of this
              command is to modify file descriptors as prescribed by the
              input/output redirection list.  In this case, any file descriptor
              numbers greater than 2 that are opened with this mechanism are
              closed when invoking another program.

       † exit [ n ]
              Causes the shell to exit with the exit status specified by n.  The
              value will be the least significant 8 bits of the specified
              status.  If n is omitted, then the exit status is that of the last
              command executed.  An end-of-file will also cause the shell to
              exit except for a shell which has the ignoreeof option (see set
              below) turned on.

       †† export [ -p ] [ name[=value] ] ...
              If name is not given, the names and values of each variable with
              the export attribute are printed with the values quoted in a
              manner that allows them to be re-input.  The export command is the
              same as typeset -x except that if you use export within a
              function, no local variable is created.  The -p option causes the
              word export to be inserted before each one.  Otherwise, the given
              names are marked for automatic export to the environment of
              subsequently-executed commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
              This command is only on systems that support job control.  Each
              job specified is brought to the foreground and waited for in the
              specified order.  Otherwise, the current job is brought into the
              foreground.  See Jobs for a description of the format of job.

       getopts [  -a name ] optstring vname [ arg ... ]
              Checks arg for legal options.  If arg is omitted, the positional
              parameters are used.  An option argument begins with a + or a -.
              An option not beginning with + or - or the argument -- ends the
              options.  Options beginning with + are only recognized when
              optstring begins with a +.  optstring contains the letters that
              getopts recognizes.  If a letter is followed by a :, that option
              is expected to have an argument.  The options can be separated
              from the argument by blanks.  The option -?  causes getopts to
              generate a usage message on standard error.  The -a argument can
              be used to specify the name to use for the usage message, which
              defaults to $0.
              getopts places the next option letter it finds inside variable
              vname each time it is invoked.  The option letter will be
              prepended with a + when arg begins with a +.  The index of the
              next arg is stored in OPTIND.  The option argument, if any, gets
              stored in OPTARG.
              A leading : in optstring causes getopts to store the letter of an
              invalid option in OPTARG, and to set vname to ?  for an unknown
              option and to : when a required option argument is missing.
              Otherwise, getopts prints an error message.  The exit status is
              non-zero when there are no more options.
              There is no way to specify any of the options :, +, -, ?, [, and
              ].  The option # can only be specified as the first option.

       hist [ -e ename  ] [ -nlr ] [ first [ last ] ]
       hist -s  [ old=new ] [ command ]
              In the first form, a range of commands from first to last is
              selected from the last HISTSIZE commands that were typed at the
              terminal.  The arguments first and last may be specified as a
              number or as a string.  A string is used to locate the most recent
              command starting with the given string.  A negative number is used
              as an offset to the current command number.  If the -l option is
              selected, the commands are listed on standard output.  Otherwise,
              the editor program ename is invoked on a file containing these
              keyboard commands.  If ename is not supplied, then the value of
              the variable HISTEDIT is used.  If HISTEDIT is not set, then
              FCEDIT (default /bin/ed) is used as the editor.  When editing is
              complete, the edited command(s) is executed if the changes have
              been saved.  If last is not specified, then it will be set to
              first.  If first is not specified, the default is the previous
              command for editing and -16 for listing.  The option -r reverses
              the order of the commands and the option -n suppresses command
              numbers when listing.  In the second form, command is interpreted
              as first described above and defaults to the last command
              executed.  The resulting command is executed after the optional
              substitution old=new is performed.

       jobs [ -lnp ] [ job ... ]
              Lists information about each given job; or all active jobs if job
              is omitted.  The -l option lists process ids in addition to the
              normal information.  The -n option only displays jobs that have
              stopped or exited since last notified.  The -p option causes only
              the process group to be listed.  See Jobs for a description of the
              format of job.

       kill [ -s signame  ] [ -q  n  ] job ...
       kill [ -n signum ] [ -q n  ] job ...
       kill -Ll  [ sig ... ]
              Sends either the TERM (terminate) signal or the specified signal
              to the specified jobs or processes.  Signals are either given by
              number with the -n option or by name with the -s option (as given
              in <signal.h>, stripped of the prefix ``SIG'' with the exception
              that SIGCLD is named CHLD).  For backward compatibility, the n and
              s can be omitted and the number or name placed immediately after
              the -.  If the signal being sent is TERM (terminate) or HUP
              (hangup), then the job or process will be sent a CONT (continue)
              signal if it is stopped.  The argument job can be the process id
              of a process that is not a member of one of the active jobs.  See
              Jobs for a description of the format of job.  In the third form,
              kill -l, or kill -L, if sig is not specified, the signal names are
              listed.  The -l option list only the signal names.  -L options
              lists each signal name and corresponding number.  Otherwise, for
              each sig that is a name, the corresponding signal number is
              listed.  For each sig that is a number, the signal name
              corresponding to the least significant 8 bits of sig is listed.
              On systems that support sigqueue(2) the -q option can be used to
              send a queued signal with message number n.  Each specified job
              must be a positive number.  On systems that do not support
              sigqueue(2), a signal is sent without the message number n and the
              signal will not be queued.  If the signal cannot be queued because
              of a return of EAGAIN, the exit status will be 2.

       let arg ...
              Each arg is a separate arithmetic expression to be evaluated.  let
              only recognizes octal constants starting with 0 when the set
              option letoctal is on.  See Arithmetic Evaluation above, for a
              description of arithmetic expression evaluation.
              The exit status is 0 if the value of the last expression is non-
              zero, and 1 otherwise.

       † newgrp [ arg ... ]
              Equivalent to exec /bin/newgrp arg ....

       print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
              With no options or with option - or --, each arg is printed on
              standard output.  The -f option causes the arguments to be printed
              as described by printf.  In this case, any e, n, r, R options are
              ignored.  Otherwise, unless the -C, -R, -r, or -v are specified,
              the following escape conventions will be applied:
              \a     The alert character (ascii 07).
              \b     The backspace character (ascii 010).
              \c     Causes print to end without processing more arguments and
                     not adding a new-line.
              \f     The formfeed character (ascii 014).
              \n     The new-line character (ascii 012).
              \r     The carriage return character (ascii 015).
              \t     The tab character (ascii 011).
              \v     The vertical tab character (ascii 013).
              \E     The escape character (ascii 033).
              \\     The backslash character \.
              \0x    The character defined by the 1, 2, or 3-digit octal string
                     given by x.

              The -R option will print all subsequent arguments and options
              other than -n.  The -e causes the above escape conventions to be
              applied.  This is the default behavior.  It reverses the effect of
              an earlier -r.  The -p option causes the arguments to be written
              onto the pipe of the process spawned with ⎪& instead of standard
              output.  The -v option treats each arg as a variable name and
              writes the value in the printf %B format.  The -C option treats
              each arg as a variable name and writes the value in the printf %#B
              format.  The -s option causes the arguments to be written onto the
              history file instead of standard output.  The -u option can be
              used to specify a one digit file descriptor unit number unit on
              which the output will be placed.  The default is 1.  If the option
              -n is used, no new-line is added to the output.

       printf [ -v varname ] format [ arg ... ]
              The arguments arg are printed on standard output in accordance
              with the ANSI-C formatting rules associated with the format string
              format.  If the number of arguments exceeds the number of format
              specifications, the format string is reused to format remaining
              arguments.  If the -v option is specified the output is assigned
              to the variable varname.  The following extensions can also be
              used:
              %b     A %b format can be used instead of %s to cause escape
                     sequences in the corresponding arg to be expanded as
                     described in print.
              %B     A %B option causes each of the arguments to be treated as
                     variable names and the binary value of variable will be
                     printed.  The alternate flag # causes a compound variable
                     to be output on a single line.  This is most useful for
                     compound variables and variables whose attribute is -b.
              %H     A %H format can be used instead of %s to cause characters
                     in arg that are special in HTML and XML to be output as
                     their entity name.  The alternate flag # formats the output
                     for use as a URI.
              %P     A %P format can be used instead of %s to cause arg to be
                     interpreted as an extended regular expression and be
                     printed as a shell pattern.
              %R     A %R format can be used instead of %s to cause arg to be
                     interpreted as a shell pattern and to be printed as an
                     extended regular expression.
              %q     A %q format can be used instead of %s to cause the
                     resulting string to be quoted in a manner than can be
                     reinput to the shell.  When q is preceded by the
                     alternative format specifier, #, the string is quoted in
                     manner suitable as a field in a .csv format file.
              %(date-format)T
                     A %(date-format)T format can be use to treat an argument as
                     a date/time string and to format the date/time according to
                     the date-format as defined for the date(1) command.  Values
                     specified as digits are interpreted as described in the
                     touch(1) command.
              %Z     A %Z format will output a byte whose value is 0.
              %d     The precision field of the %d format can be followed by a .
                     and the output base.  In this case, the # flag character
                     causes base# to be prepended.
              #      The # flag, when used with the %d format without an output
                     base, displays the output in powers of 1000 indicated by
                     one of the following suffixes: k M G T P E, and when used
                     with the %i format displays the output in powers of 1024
                     indicated by one of the following suffixes: Ki Mi Gi Ti Pi
                     Ei.
              =      The = flag centers the output within the specified field
                     width.
              L      The L flag, when used with the %c or %s formats, treats
                     precision as character width instead of byte count.
              ,      The , flag, when used with the %d or %f formats, separates
                     groups of digits with the grouping delimiter (, on groups
                     of 3 in the C locale.)

       pwd [ -LP ] [ -f fd ]
              Outputs the value of the current working directory.  The -L option
              is the default; it prints the logical name of the current
              directory.  If the -P option is given, all symbolic links are
              resolved from the name.  The last instance of -L or -P on the
              command line determines which method is used.  If the -f option is
              specified, the directory name corresponding to file descriptor fd
              is outputted.

       read [ -AaCSprsv ] [ -d delim] [ -n n] [ -N n] [ -m method] [ -t timeout]
       [ -u unit] [ vname?prompt ] [ vname ... ]
              The shell input mechanism.  One line is read and is broken up into
              fields using the characters in IFS as separators.  The escape
              character, \, is used to remove any special meaning for the next
              character and for line continuation.  The -d option causes the
              read to continue to the first character of delim rather than new-
              line.  The -n option causes at most n bytes to read rather a full
              line but will return when reading from a slow device as soon as
              any characters have been read.  The -N option causes exactly n to
              be read unless an end-of-file has been encountered or the read
              times out because of the -t option.  In raw mode, -r, the \
              character is not treated specially.  The first field is assigned
              to the first vname, the second field to the second vname, etc.,
              with leftover fields assigned to the last vname.  When vname has
              the binary attribute and -n or -N is specified, the bytes that are
              read are stored directly into the variable.  If the -v is
              specified, then the value of the first vname will be used as a
              default value when reading from a terminal device.  The -A option
              causes the variable vname to be unset and each field that is read
              to be stored in successive elements of the indexed array vname.
              -a is an alias for -A.  The -m option reads a compound variable
              with the read method defined by method.  Currently, only the json
              and ksh methods exist.  The -C option causes the variable vname to
              be read as a compound variable.  Blanks will be ignored when
              finding the beginning open parenthesis.  This is equivalent to -m
              ksh.  The -S option causes the line to be treated like a record in
              a .csv format file so that double quotes can be used to allow the
              delimiter character and the new-line character to appear within a
              field.  The -p option causes the input line to be taken from the
              input pipe of a process spawned by the shell using ⎪&.  If the -s
              option is present, the input will be saved as a command in the
              history file.  The option -u can be used to specify a one digit
              file descriptor unit unit to read from.  The file descriptor can
              be opened with the exec special built-in command.  The default
              value of unit n is 0.  The option -t is used to specify a timeout
              in seconds when reading from a terminal or pipe.  If vname is
              omitted, then REPLY is used as the default vname.  An end-of-file
              with the -p option causes cleanup for this process so that another
              can be spawned.  If the first argument contains a ?, the remainder
              of this word is used as a prompt on standard error when the shell
              is interactive.  The exit status is 0 unless an end-of-file is
              encountered or read has timed out.

       †† readonly [ -p ] [ vname[=value] ] ...
              If vname is not given, the names and values of each variable with
              the readonly attribute is printed with the values quoted in a
              manner that allows them to be re-inputted.  The -p option causes
              the word readonly to be inserted before each one.  Otherwise, the
              given vnames are marked readonly and these names cannot be changed
              by subsequent assignment.  When defining a type, if the value of a
              readonly sub-variable is not defined the value is required when
              creating each instance.

       † return [ n ]
              Causes a shell function or .  script to return to the invoking
              script with the exit status specified by n.  The value will be the
              least significant 8 bits of the specified status.  If n is
              omitted, then the return status is that of the last command
              executed.  If return is invoked while not in a function or a .
              script, then it behaves the same as exit.

       † set [ ±BCGabefhkmnoprstuvx ] [ ±o [ option ] ] ... [ ±A vname ]  [ -K
       keylist ] [ arg ... ]
              The options for this command have meaning as follows:
              -A      Array assignment.  If arg is specified, unset the variable
                      vname and assign values sequentially from the arg list.
                      If +A is used, the variable vname is not unset first.
              -B      Enable brace group expansion.  On by default.
              -C      Prevents redirection > from truncating existing files.
                      Files that are created are opened with the O_EXCL mode.
                      Requires >⎪ to truncate a file when turned on.
              -G      Causes the pattern ** by itself to match files and zero or
                      more directories and sub-directories when used for file
                      name generation.  If followed by a / only directories and
                      sub-directories are matched.
              -H      Enable !-style history expansion similar to csh(1).
              -K      When no arguments are specified, it is used along with -s
                      to specify the sort fields and sort options for sorting an
                      array.  (See "Array Sorting" above for the description of
                      the keylist option.)
              -a      All subsequent variables that are defined are
                      automatically exported.
              -b      Prints job completion messages as soon as a background job
                      changes state rather than waiting for the next prompt.
              -e      Unless contained in a ⎪⎪ or && command, or the command
                      following an if while or until command or in the pipeline
                      following !, if a command has a non-zero exit status,
                      execute the ERR trap, if set, and exit.  This mode is
                      disabled while reading profiles.
              -f      Disables file name generation.
              -h      Each command becomes a tracked alias when first
                      encountered.
              -k      (Obsolete). All variable assignment arguments are placed
                      in the environment for a command, not just those that
                      precede the command name.
              -m      Background jobs will run in a separate process group and a
                      line will print upon completion.  The exit status of
                      background jobs is reported in a completion message.  On
                      systems with job control, this option is turned on
                      automatically for interactive shells.
              -n      Read commands and check them for syntax errors, but do not
                      execute them.  Ignored for interactive shells.
              -o      The following argument can be one of the following option
                      names:
                      allexport
                              Same as -a.
                      bgnice  All background jobs are run at a lower priority.
                              This is the default mode.
                      braceexpand
                              Same as -B.
                      emacs   Puts you in an emacs style in-line editor for
                              command entry.
                      errexit Same as -e.
                      globstar
                              Same as -G.
                      gmacs   Puts you in a gmacs style in-line editor for
                              command entry.
                      histexpand
                              Same as -H.
                      ignoreeof
                              The shell will not exit on end-of-file.  The
                              command exit must be used.
                      keyword Same as -k.
                      letoctal
                              The let command allows octal constants starting
                              with 0.
                      markdirs
                              All directory names resulting from file name
                              generation have a trailing / appended.
                      monitor Same as -m.
                      multiline
                              The built-in editors will use multiple lines on
                              the screen for lines that are longer than the
                              width of the screen.  This may not work for all
                              terminals.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Do not save function definitions in the history
                              file.
                      notify  Same as -b.
                      nounset Same as -u.
                      pipefail
                              A pipeline will not complete until all components
                              of the pipeline have completed, and the return
                              value will be the value of the last non-zero
                              command to fail or zero if no command has failed.
                      privileged
                              Same as -p.
                      showme  When enabled, simple commands or pipelines
                              preceded by a semicolon (;) will be displayed as
                              if the xtrace option were enabled but will not be
                              executed.  Otherwise, the leading ; will be
                              ignored.
                      trackall
                              Same as -h.
                      verbose Same as -v.
                      vi      Puts you in insert mode of a vi style in-line
                              editor until you hit the escape character 033.
                              This puts you in control mode.  A return sends the
                              line.
                      viraw   Each character is processed as it is typed in vi
                              mode.  This is now always enabled. Disabling the
                              option at run time has no effect.
                      xtrace  Same as -x.
                      If no option name is supplied, then the current option
                      settings are printed.
              -p      Disables processing of the $HOME/.profile file and uses
                      the file /etc/suid_profile instead of the ENV file.  This
                      mode is on whenever the effective uid (gid) is not equal
                      to the real uid (gid).  Turning this off causes the
                      effective uid and gid to be set to the real uid and gid.
              -r      Enables the restricted shell.  This option cannot be unset
                      once set.
              -s      Sort the positional parameters lexicographically.  When
                      used with -A
              sorts the elements of the array.
                      -t (Obsolete).  Exit after reading and executing one
                      command.
              -u      Treat unset parameters as an error when substituting.
              -v      Print shell input lines as they are read.
              -x      Print commands and their arguments as they are executed.
              --      Do not change any of the options; useful in setting $1 to
                      a value beginning with -.  If no arguments follow this
                      option then the positional parameters are unset.

              As an obsolete feature, if the first arg is - then the -x and -v
              options are turned off and the next arg is treated as the first
              argument.  Using + rather than - causes these options to be turned
              off.  These options can also be used upon invocation of the shell.
              The current set of options may be found in $-.  Unless -A is
              specified, the remaining arguments are positional parameters and
              are assigned, in order, to $1 $2 ....  If no arguments are given,
              then the names and values of all variables are printed on the
              standard output.

       † shift [ n ]
              The positional parameters from $n+1 ...  are renamed $1 ... ,
              default n is 1.  The parameter n can be any arithmetic expression
              that evaluates to a non-negative number less than or equal to $#.

       sleep seconds
              Suspends execution for the number of decimal seconds or fractions
              of a second given by seconds.  seconds A suffix of one of smhd can
              be used to indicate seconds, minutes, hours, and days
              respectively.  Seconds can also be specified using a date/time
              format.

       times  Display CPU time used by the shell and all of its child processes.

       † trap [ -alp ] [ action ] [ sig ] ...
              The -p option causes the trap action associated with each trap as
              specified by the arguments to be printed with appropriate quoting.
              Otherwise, action will be processed as if it were an argument to
              eval when the shell receives signal(s) sig.
              The -a option causes the current trap setting to be appended to
              action.  Each sig can be given as a number or as the name of the
              signal.  Trap commands are executed in order of signal number.
              Any attempt to set a trap on a signal that was ignored on entry to
              the current shell is ineffective.  If action is omitted and the
              first sig is a number, or if action is -, then the trap(s) for
              each sig are reset to their original values.  If action is the
              null string then this signal is ignored by the shell and by the
              commands it invokes.
              If sig is ERR then action will be executed whenever a command has
              a non-zero exit status.
              If sig is DEBUG then action will be executed before each command.
              The variable .sh.command will contain the contents of the current
              command line when action is running.  If the exit status of the
              trap is 2 the command will not be executed.  If the exit status of
              the trap is 255 and inside a function or a dot script, the
              function or dot script will return.
              If sig is 0 or EXIT and the trap statement is executed inside the
              body of a function defined with the function name syntax, then the
              command action is executed after the function completes.  For a
              trap set outside any function then the command action is executed
              on exit from the shell.
              If sig is KEYBD, then action will be executed whenever a key is
              read while in emacs, gmacs, or vi mode.  The trap command with no
              arguments prints a list of commands associated with each signal
              number.
              An exit or return without an argument in a trap action will
              preserve the exit status of the command that invoked the trap.
              action.  Each sig can be given as a number or as the name of the
              signal.  Trap commands are executed in order of signal number.
              Any attempt to set a trap on a signal that was ignored on entry to
              the current shell is ineffective.  If action is omitted and the
              first sig is a number, or if action is -, then the trap(s) for
              each sig are reset to their original values.  The -l option lists
              the signals and their numbers to standard output.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       †† typeset [ ±ACHSfblmnprstux ] [ ±EFLRXZi[n] ]   [ +-M  [ mapname ] ] [
       -T  [ tname=(assign_list) ] ] [ -h str ] [ -a [type] ] [ vname[=value ]
       ] ...
              Sets attributes and values for shell variables and functions.
              When invoked inside a function defined with the function name
              syntax, a new instance of the variable vname is created, and the
              variable's value and type are restored when the function
              completes.  The following list of attributes may be specified:
              -A     Declares vname to be an associative array.  Subscripts are
                     strings rather than arithmetic expressions.
              -C     causes each vname to be a compound variable.  value names a
                     compound variable it is copied into vname.  Otherwise, it
                     unsets each vname.
              -a     Declares vname to be an indexed array.  If type is
                     specified, it must be the name of an enumeration type
                     created with the enum command and it allows enumeration
                     constants to be used as subscripts.
              -E     Declares vname to be a double precision floating point
                     number.  If n is non-zero, it defines the number of
                     significant figures that are used when expanding vname.
                     Otherwise, ten significant figures will be used.
              -F     Declares vname to be a double precision floating point
                     number.  If n is non-zero, it defines the number of places
                     after the decimal point that are used when expanding vname.
                     Otherwise ten places after the decimal point will be used.
              -H     This option provides UNIX to host-name file mapping on non-
                     UNIX machines.
              -L     Left justify and remove leading blanks from value.  If n is
                     non-zero, it defines the width of the field, otherwise it
                     is determined by the width of the value of first
                     assignment.  When the variable is assigned to, it is filled
                     on the right with blanks or truncated, if necessary, to fit
                     into the field.  The -R option is turned off.
              -M     Use the character mapping mapping defined by wctrans(3).
                     such as tolower and toupper when assigning a value to each
                     of the specified operands.  When mapping is specified and
                     there are not operands, all variables that use this mapping
                     are written to standard output.  When mapping is omitted
                     and there are no operands, all mapped variables are written
                     to standard output.
              -R     Right justify and fill with leading blanks.  If n is non-
                     zero, it defines the width of the field, otherwise it is
                     determined by the width of the value of first assignment.
                     The field is left filled with blanks or truncated from the
                     end if the variable is reassigned.  The -L option is turned
                     off.
              -S     When used within the assign_list of a type definition, it
                     causes the specified sub-variable to be shared by all
                     instances of the type.  When used inside a function defined
                     with the function reserved word, the specified variables
                     will have function static scope.  Otherwise, the variable
                     is unset prior to processing the assignment list.
              -T     If followed by tname, it creates a type named by tname
                     using the compound assignment assign_list to tname.
                     Otherwise, it writes all the type definitions to standard
                     output.
              -X     Declares vname to be a double precision floating point
                     number and expands using the %a format of ISO-C99.  If n is
                     non-zero, it defines the number of hex digits after the
                     radix point that is used when expanding vname.  The default
                     is 10.
              -Z     Right justify and fill with leading zeros if the first non-
                     blank character is a digit and the -L option has not been
                     set.  Remove leading zeros if the -L option is also set.
                     If n is non-zero, it defines the width of the field,
                     otherwise it is determined by the width of the value of
                     first assignment.
              -f     The names refer to function names rather than variable
                     names.  No assignments can be made and the only other valid
                     options are -S, -t, -u and -x.  The -S can be used with
                     discipline functions defined in a type to indicate that the
                     function is static.  For a static function, the same method
                     will be used by all instances of that type no matter which
                     instance references it.  In addition, it can only use value
                     of variables from the original type definition.  These
                     discipline functions cannot be redefined in any type
                     instance.  The -t option turns on execution tracing for
                     this function.  The -u option causes this function to be
                     marked undefined.  The FPATH variable will be searched to
                     find the function definition when the function is
                     referenced.  If no options other than -f is specified, then
                     the function definition will be displayed on standard
                     output.  If +f is specified, then a line containing the
                     function name followed by a shell comment containing the
                     line number and path name of the file where this function
                     was defined, if any, is displayed.  The exit status can be
                     used to determine whether the function is defined so that
                     typeset -f .sh.math.name will return 0 when math function
                     name is defined and non-zero otherwise.
              -b     The variable can hold any number of bytes of data.  The
                     data can be text or binary.  The value is represented by
                     the base64 encoding of the data.  If -Z is also specified,
                     the size in bytes of the data in the buffer will be
                     determined by the size associated with the -Z.  If the
                     base64 string assigned results in more data, it will be
                     truncated.  Otherwise, it will be filled with bytes whose
                     value is zero.  The printf format %B can be used to output
                     the actual data in this buffer instead of the base64
                     encoding of the data.
              -h     Used within type definitions to add information when
                     generating information about the sub-variable on the man
                     page.  It is ignored when used outside of a type
                     definition.  When used with -f the information is
                     associated with the corresponding discipline function.
              -i     Declares vname to be represented internally as integer.
                     The right hand side of an assignment is evaluated as an
                     arithmetic expression when assigning to an integer.  If n
                     is non-zero, it defines the output arithmetic base,
                     otherwise the output base will be ten.
              -l     Used with -i, -E or -F, to indicate long integer, or long
                     double.  Otherwise, all upper-case characters are converted
                     to lower-case.  The upper-case option, -u, is turned off.
                     Equivalent to -M tolower .
              -m     moves or renames the variable.  The value is the name of a
                     variable whose value will be moved to vname.  The original
                     variable will be unset.  Cannot be used with any other
                     options.
              -n     Declares vname to be a reference to the variable whose name
                     is defined by the value of variable vname.  This is usually
                     used to reference a variable inside a function whose name
                     has been passed as an argument.  Cannot be used with any
                     other options.
              -p     The name, attributes and values for the given vnames are
                     written on standard output in a form that can be used as
                     shell input.  If +p is specified, then the values are not
                     displayed.
              -r     The given vnames are marked readonly and these names cannot
                     be changed by subsequent assignment.
              -s     Used with -i, -E or -F, to indicate short integer, or
                     float.
              -t     Tags the variables.  Tags are user definable and have no
                     special meaning to the shell.
              -u     When given along with -i, specifies unsigned integer.
                     Otherwise, all lower-case characters are converted to
                     upper-case.  The lower-case option, -l, is turned off.
                     Equivalent to -M toupper .
              -x     The given vnames are marked for automatic export to the
                     environment of subsequently-executed commands.  Variables
                     whose names contain a .  cannot be exported.

              The -i attribute cannot be specified along with -R, -L, -Z, or -f.

              Using + rather than - causes these options to be turned off.  If
              no vname arguments are given, a list of vnames (and optionally the
              values) of the variables is printed.  (Using + rather than - keeps
              the values from being printed.)  The -p option causes typeset
              followed by the option letters to be printed before each name
              rather than the names of the options.  If any option other than -p
              is given, only those variables which have all of the given options
              are printed.  Otherwise, the vnames and attributes of all
              variables that have attributes are printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
              Set or display a resource limit.  The available resource limits
              are listed below.  Many systems do not support one or more of
              these limits.  The limit for a specified resource is set when
              limit is specified.  The value of limit can be a number in the
              unit specified below with each resource, or the value unlimited.
              The -H and -S options specify whether the hard limit or the soft
              limit for the given resource is set.  A hard limit cannot be
              increased once it is set.  A soft limit can be increased up to the
              value of the hard limit.  If neither the H nor S option is
              specified, the limit applies to both.  The current resource limit
              is printed when limit is omitted.  In this case, the soft limit is
              printed unless H is specified.  When more than one resource is
              specified, then the limit name and unit is printed before the
              value.
              -a     Lists all of the current resource limits.
              -c     The number of 512-byte blocks on the size of core dumps.
              -d     The number of K-bytes on the size of the data area.
              -f     The number of 512-byte blocks on files that can be written
                     by the current process or by child processes (files of any
                     size may be read).
              -m     The number of K-bytes on the size of physical memory.
              -n     The number of file descriptors plus 1.
              -p     The number of 512-byte blocks for pipe buffering.
              -s     The number of K-bytes on the size of the stack area.
              -t     The number of CPU seconds to be used by each process.
              -v     The number of K-bytes for virtual memory.

              If no option is given, -f is assumed.

       umask [ -pS ] [ mask ]
              The user file-creation mask is set to mask (see umask(2)).  mask
              can either be an octal number or a symbolic value as described in
              chmod(1).  If a symbolic value is given, the new umask value is
              the complement of the result of applying mask to the complement of
              the previous umask value.  If mask is omitted, the current value
              of the mask is printed.  The -S option causes the mode to be
              printed as a symbolic value.  Otherwise, the mask is printed in
              octal.  The -p option cause the output to be in a form that can be
              use for reinput.

       † unalias [ -a ] name ...
              The aliases given by the list of names are removed from the alias
              list.  The -a option causes all the aliases to be unset.

       †unset [ -fnv ] vname ...
              The variables given by the list of vnames are unassigned, i.e.,
              except for sub-variables within a type, their values and
              attributes are erased.  For sub-variables of a type, the values
              are reset to the default value from the type definition.  Readonly
              variables cannot be unset.  If the -f option is set, then the
              names refer to function names.  If the -v option is set, then the
              names refer to variable names.  The -f option overrides -v.  If -n
              is set and name is a name reference, then name will be unset
              rather than the variable that it references.  The default is
              equivalent to -v.  Unsetting LINENO, MAILCHECK, OPTARG, OPTIND,
              RANDOM, SECONDS, TMOUT, and _ removes their special meaning even
              if they are subsequently assigned to.

       wait [ job ... ]
              Wait for the specified job and report its termination status.  If
              job is not given, then all currently active child processes are
              waited for.  The exit status from this command is that of the last
              process waited for if job is specified; otherwise it is zero.  See
              Jobs for a description of the format of job.

       whence [ -afpv ] name ...
              For each name, indicate how it would be interpreted if used as a
              command name.
              The -v option produces a more verbose report.  The -f option skips
              the search for functions.  The -p option does a path search for
              name even if name is an alias, a function, or a reserved word.
              The -p option turns off the -v option.  The -a option is similar
              to the -v option but causes all interpretations of the given name
              to be reported.

   Invocation.
       If the shell is invoked by exec(2), and the first character of argument
       zero ($0) is -, then the shell is assumed to be a login shell and
       commands are read from /etc/profile and then from $HOME/.profile, if it
       exists.  Alternatively, the option -l causes the shell to a treated as a
       login shell.  Next, for interactive shells, commands are read from the
       file named by performing parameter expansion, command substitution, and
       arithmetic substitution on the value of the environment variable ENV if
       the file exists.  If the -s option is not present and arg and a file by
       the name of arg exists, then it reads and executes this script.
       Otherwise, if the first arg does not contain a /, a path search is
       performed on the first arg to determine the name of the script to
       execute.  The script arg must have execute permission and any setuid and
       setgid settings will be ignored.  If the script is not found on the path,
       arg is processed as if it named a built-in command or function.  Commands
       are then read as described below; the following options are interpreted
       by the shell when it is invoked:

       -D      A list of all double quoted strings that are preceded by a $ will
               be printed on standard output and the shell will exit.  This set
               of strings will be subject to language translation when the
               locale is not C or POSIX.  No commands will be executed.

       -E      Reads the file named by the ENV variable or by $HOME/.kshrc if
               not defined after the profiles.

       -c      If the -c option is present, then commands are read from the
               first arg.  Any remaining arguments become positional parameters
               starting at 0.

       -s      If the -s option is present or if no arguments remain, then
               commands are read from the standard input.  Shell output, except
               for the output of the Special Commands listed above, is written
               to file descriptor 2.

       -i      If the -i option is present or if the shell input and error
               output are attached to a terminal (as told by tcgetattr(2)), then
               this shell is interactive.  In this case TERM is ignored (so that
               kill 0 does not kill an interactive shell) and INTR is caught and
               ignored (so that wait is interruptible).  In all cases, QUIT is
               ignored by the shell.

       -r      If the -r option is present, the shell is a restricted shell.

       -P      If -P or -o profile is present, the shell is a profile shell (see
               pfexec(1)).

       -R filename
               The -R filename option is used to generate a cross reference
               database that can be used by a separate utility to find
               definitions and references for variables and commands.  The
               filename argument specifies the generated database. A script file
               must be provided on the command line as well.

       The remaining options and arguments are described under the set command
       above.  An optional - as the first argument is ignored.

   Rksh Only.
       Rksh is used to set up login names and execution environments whose
       capabilities are more controlled than those of the standard shell.  The
       actions of rksh are identical to those of ksh, except that the following
       are disallowed:
              Unsetting the restricted option.
              changing directory (see cd(1)),
              setting or unsetting the value or attributes of SHELL, ENV, FPATH,
              or PATH,
              specifying path or command names containing /,
              redirecting output (>, >|, <>, and >>).
              adding or deleting built-in commands.
              using command -p to invoke a command.

       The restrictions above are enforced after .profile and the ENV files are
       interpreted.

       When a command to be executed is found to be a shell procedure, rksh
       invokes ksh to execute it.  Thus, it is possible to provide to the end-
       user shell procedures that have access to the full power of the standard
       shell, while imposing a limited menu of commands; this scheme assumes
       that the end-user does not have write and execute permissions in the same
       directory.

       The net effect of these rules is that the writer of the .profile has
       complete control over user actions, by performing guaranteed setup
       actions and leaving the user in an appropriate directory (probably not
       the login directory).

       The system administrator often sets up a directory of commands (e.g.,
       /usr/rbin) that can be safely invoked by rksh.

EXIT STATUS
       Errors detected by the shell, such as syntax errors, cause the shell to
       return a non-zero exit status.  If the shell is being used non-
       interactively, then execution of the shell file is abandoned unless the
       error occurs inside a subshell in which case the subshell is abandoned.
       Otherwise, the shell returns the exit status of the last command executed
       (see also the exit command above).  Run time errors detected by the shell
       are reported by printing the command or function name and the error
       condition.  If the line number that the error occurred on is greater than
       one, then the line number is also printed in square brackets ([]) after
       the command or function name.

FILES
       /etc/profile
              The system wide initialization file, executed for login shells.

       $HOME/.profile
              The personal initialization file, executed for login shells after
              /etc/profile.

       $HOME/.kshrc
              Default personal initialization file, executed for interactive
              shells when ENV is not set.

       /etc/suid_profile
              Alternative initialization file, executed instead of the personal
              initialization file when the real and effective user or group id
              do not match.

       /dev/null
              NULL device

SEE ALSO
       cat(1), cd(1), chmod(1), cut(1), date(1), egrep(1), echo(1), emacs(1),
       env(1), fgrep(1), gmacs(1), grep(1), newgrp(1), pfexec(1), stty(1),
       test(1), touch(1), umask(1), vi(1), dup(2), exec(2), fork(2),
       getpwnam(3), ioctl(2), lseek(2), paste(1), pathconf(2), pipe(2),
       sigsetinfo(2), sysconf(2), umask(2), ulimit(2), wait(2), wctrans(3),
       rand(3), a.out(5), profile(5), environ(7).

       Morris I. Bolsky and David G. Korn, The New KornShell Command and
       Programming Language, Prentice Hall, 1995.

       POSIX - Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC
       9945-2, IEEE, 1993.

CAVEATS
       If a command is executed, and then a command with the same name is
       installed in a directory in the search path before the directory where
       the original command was found, the shell will continue to exec the
       original command.  Use the -t option of the alias command to correct this
       situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe
       character .

       Using the hist built-in command within a compound command will cause the
       whole command to disappear from the history file.

       The built-in command . file reads the whole file before any commands are
       executed.  Therefore, alias and unalias commands in the file will not
       apply to any commands defined in the file.

       Traps are not processed while a job is waiting for a foreground process.
       Thus, a trap on CHLD won't be executed until the foreground job
       terminates.

       It is a good idea to leave a space after the comma operator in arithmetic
       expressions to prevent the comma from being interpreted as the decimal
       point character in certain locales.



                                                                          KSH(1)