awk

GAWK(1)                        Utility Commands                        GAWK(1)



NAME
       gawk - pattern scanning and processing language

SYNOPSIS
       gawk [ POSIX or GNU style options ] -f program-file [ -- ] file ...
       gawk [ POSIX or GNU style options ] [ -- ] program-text file ...

DESCRIPTION
       Gawk is the GNU Project's implementation of the AWK programming
       language.  It conforms to the definition of the language in the POSIX
       1003.1 standard.  This version in turn is based on the description in
       The AWK Programming Language, by Aho, Kernighan, and Weinberger.  Gawk
       provides the additional features found in the current version of Brian
       Kernighan's awk and numerous GNU-specific extensions.

       The command line consists of options to gawk itself, the AWK program
       text (if not supplied via the -f or -i options), and values to be made
       available in the ARGC and ARGV pre-defined AWK variables.

       When gawk is invoked with the --profile option, it starts gathering
       profiling statistics from the execution of the program.  Gawk runs more
       slowly in this mode, and automatically produces an execution profile in
       the file awkprof.out when done.  See the --profile option, below.

       Gawk also has an integrated debugger. An interactive debugging session
       can be started by supplying the --debug option to the command line. In
       this mode of execution, gawk loads the AWK source code and then prompts
       for debugging commands.  Gawk can only debug AWK program source
       provided with the -f option.  The debugger is documented in GAWK:
       Effective AWK Programming.

OPTION FORMAT
       Gawk options may be either traditional POSIX-style one letter options,
       or GNU-style long options.  POSIX options start with a single “-”,
       while long options start with “--”.  Long options are provided for both
       GNU-specific features and for POSIX-mandated features.

       Gawk-specific options are typically used in long-option form.
       Arguments to long options are either joined with the option by an =
       sign, with no intervening spaces, or they may be provided in the next
       command line argument.  Long options may be abbreviated, as long as the
       abbreviation remains unique.

       Additionally, every long option has a corresponding short option, so
       that the option's functionality may be used from within #!  executable
       scripts.

OPTIONS
       Gawk accepts the following options.  Standard options are listed first,
       followed by options for gawk extensions, listed alphabetically by short
       option.

       -f program-file
       --file program-file
              Read the AWK program source from the file program-file, instead
              of from the first command line argument.  Multiple -f (or
              --file) options may be used.

       -F fs
       --field-separator fs
              Use fs for the input field separator (the value of the FS
              predefined variable).

       -v var=val
       --assign var=val
              Assign the value val to the variable var, before execution of
              the program begins.  Such variable values are available to the
              BEGIN rule of an AWK program.

       -b
       --characters-as-bytes
              Treat all input data as single-byte characters. In other words,
              don't pay any attention to the locale information when
              attempting to process strings as multibyte characters.  The
              --posix option overrides this one.

       -c
       --traditional
              Run in compatibility mode.  In compatibility mode, gawk behaves
              identically to Brian Kernighan's awk; none of the GNU-specific
              extensions are recognized.  See GNU EXTENSIONS, below, for more
              information.

       -C
       --copyright
              Print the short version of the GNU copyright information message
              on the standard output and exit successfully.

       -d[file]
       --dump-variables[=file]
              Print a sorted list of global variables, their types and final
              values to file.  If no file is provided, gawk uses a file named
              awkvars.out in the current directory.
              Having a list of all the global variables is a good way to look
              for typographical errors in your programs.  You would also use
              this option if you have a large program with a lot of functions,
              and you want to be sure that your functions don't inadvertently
              use global variables that you meant to be local.  (This is a
              particularly easy mistake to make with simple variable names
              like i, j, and so on.)

       -D[file]
       --debug[=file]
              Enable debugging of AWK programs.  By default, the debugger
              reads commands interactively from the keyboard (standard input).
              The optional file argument specifies a file with a list of
              commands for the debugger to execute non-interactively.

       -e program-text
       --source program-text
              Use program-text as AWK program source code.  This option allows
              the easy intermixing of library functions (used via the -f and
              -i options) with source code entered on the command line.  It is
              intended primarily for medium to large AWK programs used in
              shell scripts.

       -E file
       --exec file
              Similar to -f, however, this is option is the last one
              processed.  This should be used with #!  scripts, particularly
              for CGI applications, to avoid passing in options or source code
              (!) on the command line from a URL.  This option disables
              command-line variable assignments.

       -g
       --gen-pot
              Scan and parse the AWK program, and generate a GNU .pot
              (Portable Object Template) format file on standard output with
              entries for all localizable strings in the program.  The program
              itself is not executed.  See the GNU gettext distribution for
              more information on .pot files.

       -h
       --help Print a relatively short summary of the available options on the
              standard output.  (Per the GNU Coding Standards, these options
              cause an immediate, successful exit.)

       -i include-file
       --include include-file
              Load an awk source library.  This searches for the library using
              the AWKPATH environment variable.  If the initial search fails,
              another attempt will be made after appending the .awk suffix.
              The file will be loaded only once (i.e., duplicates are
              eliminated), and the code does not constitute the main program
              source.

       -l lib
       --load lib
              Load a gawk extension from the shared library lib.  This
              searches for the library using the AWKLIBPATH environment
              variable.  If the initial search fails, another attempt will be
              made after appending the default shared library suffix for the
              platform.  The library initialization routine is expected to be
              named dl_load().

       -L [value]
       --lint[=value]
              Provide warnings about constructs that are dubious or non-
              portable to other AWK implementations.  With an optional
              argument of fatal, lint warnings become fatal errors.  This may
              be drastic, but its use will certainly encourage the development
              of cleaner AWK programs.  With an optional argument of invalid,
              only warnings about things that are actually invalid are issued.
              (This is not fully implemented yet.)

       -M
       --bignum
              Force arbitrary precision arithmetic on numbers. This option has
              no effect if gawk is not compiled to use the GNU MPFR and MP
              libraries.  (In such a case, gawk issues a warning.)

       -n
       --non-decimal-data
              Recognize octal and hexadecimal values in input data.  Use this
              option with great caution!

       -N
       --use-lc-numeric
              Force gawk to use the locale's decimal point character when
              parsing input data.  Although the POSIX standard requires this
              behavior, and gawk does so when --posix is in effect, the
              default is to follow traditional behavior and use a period as
              the decimal point, even in locales where the period is not the
              decimal point character.  This option overrides the default
              behavior, without the full draconian strictness of the --posix
              option.

       -o[file]
       --pretty-print[=file]
              Output a pretty printed version of the program to file.  If no
              file is provided, gawk uses a file named awkprof.out in the
              current directory.  Implies --no-optimize.

       -O
       --optimize
              Enable gawk's default optimizations upon the internal
              representation of the program.  Currently, this includes simple
              constant-folding, and tail call elimination for recursive
              functions.  This option is on by default.

       -p[prof-file]
       --profile[=prof-file]
              Start a profiling session, and send the profiling data to prof-
              file.  The default is awkprof.out.  The profile contains
              execution counts of each statement in the program in the left
              margin and function call counts for each user-defined function.
              Implies --no-optimize.

       -P
       --posix
              This turns on compatibility mode, with the following additional
              restrictions:

              · \x escape sequences are not recognized.

              · You cannot continue lines after ?  and :.

              · The synonym func for the keyword function is not recognized.

              · The operators ** and **= cannot be used in place of ^ and ^=.

       -r
       --re-interval
              Enable the use of interval expressions in regular expression
              matching (see Regular Expressions, below).  Interval expressions
              were not traditionally available in the AWK language.  The POSIX
              standard added them, to make awk and egrep consistent with each
              other.  They are enabled by default, but this option remains for
              use with --traditional.

       -s
       --no-optimize
              Disable gawk's default optimizations upon the internal
              representation of the program.

       -S
       --sandbox
              Run gawk in sandbox mode, disabling the system() function, input
              redirection with getline, output redirection with print and
              printf, and loading dynamic extensions.  Command execution
              (through pipelines) is also disabled.  This effectively blocks a
              script from accessing local resources, except for the files
              specified on the command line.

       -t
       --lint-old
              Provide warnings about constructs that are not portable to the
              original version of UNIX awk.

       -V
       --version
              Print version information for this particular copy of gawk on
              the standard output.  This is useful mainly for knowing if the
              current copy of gawk on your system is up to date with respect
              to whatever the Free Software Foundation is distributing.  This
              is also useful when reporting bugs.  (Per the GNU Coding
              Standards, these options cause an immediate, successful exit.)

       --     Signal the end of options. This is useful to allow further
              arguments to the AWK program itself to start with a “-”.  This
              provides consistency with the argument parsing convention used
              by most other POSIX programs.

       In compatibility mode, any other options are flagged as invalid, but
       are otherwise ignored.  In normal operation, as long as program text
       has been supplied, unknown options are passed on to the AWK program in
       the ARGV array for processing.  This is particularly useful for running
       AWK programs via the #!  executable interpreter mechanism.

       For POSIX compatibility, the -W option may be used, followed by the
       name of a long option.

AWK PROGRAM EXECUTION
       An AWK program consists of a sequence of optional directives, pattern-
       action statements, and optional function definitions.

              @include "filename"
              @load "filename"
              pattern   { action statements }
              function name(parameter list) { statements }

       Gawk first reads the program source from the program-file(s) if
       specified, from arguments to --source, or from the first non-option
       argument on the command line.  The -f and --source options may be used
       multiple times on the command line.  Gawk reads the program text as if
       all the program-files and command line source texts had been
       concatenated together.  This is useful for building libraries of AWK
       functions, without having to include them in each new AWK program that
       uses them.  It also provides the ability to mix library functions with
       command line programs.

       In addition, lines beginning with @include may be used to include other
       source files into your program, making library use even easier.  This
       is equivalent to using the -i option.

       Lines beginning with @load may be used to load extension functions into
       your program.  This is equivalent to using the -l option.

       The environment variable AWKPATH specifies a search path to use when
       finding source files named with the -f and -i options.  If this
       variable does not exist, the default path is ".:/usr/local/share/awk".
       (The actual directory may vary, depending upon how gawk was built and
       installed.)  If a file name given to the -f option contains a “/”
       character, no path search is performed.

       The environment variable AWKLIBPATH specifies a search path to use when
       finding source files named with the -l option.  If this variable does
       not exist, the default path is "/usr/local/lib/gawk".  (The actual
       directory may vary, depending upon how gawk was built and installed.)

       Gawk executes AWK programs in the following order.  First, all variable
       assignments specified via the -v option are performed.  Next, gawk
       compiles the program into an internal form.  Then, gawk executes the
       code in the BEGIN rule(s) (if any), and then proceeds to read each file
       named in the ARGV array (up to ARGV[ARGC-1]).  If there are no files
       named on the command line, gawk reads the standard input.

       If a filename on the command line has the form var=val it is treated as
       a variable assignment.  The variable var will be assigned the value
       val.  (This happens after any BEGIN rule(s) have been run.)  Command
       line variable assignment is most useful for dynamically assigning
       values to the variables AWK uses to control how input is broken into
       fields and records.  It is also useful for controlling state if
       multiple passes are needed over a single data file.

       If the value of a particular element of ARGV is empty (""), gawk skips
       over it.

       For each input file, if a BEGINFILE rule exists, gawk executes the
       associated code before processing the contents of the file. Similarly,
       gawk executes the code associated with ENDFILE after processing the
       file.

       For each record in the input, gawk tests to see if it matches any
       pattern in the AWK program.  For each pattern that the record matches,
       gawk executes the associated action.  The patterns are tested in the
       order they occur in the program.

       Finally, after all the input is exhausted, gawk executes the code in
       the END rule(s) (if any).

   Command Line Directories
       According to POSIX, files named on the awk command line must be text
       files.  The behavior is ``undefined'' if they are not.  Most versions
       of awk treat a directory on the command line as a fatal error.

       Starting with version 4.0 of gawk, a directory on the command line
       produces a warning, but is otherwise skipped.  If either of the --posix
       or --traditional options is given, then gawk reverts to treating
       directories on the command line as a fatal error.

VARIABLES, RECORDS AND FIELDS
       AWK variables are dynamic; they come into existence when they are first
       used.  Their values are either floating-point numbers or strings, or
       both, depending upon how they are used.  Additionally, gawk allows
       variables to have regular-expression type.  AWK also has one
       dimensional arrays; arrays with multiple dimensions may be simulated.
       Gawk provides true arrays of arrays; see Arrays, below.  Several pre-
       defined variables are set as a program runs; these are described as
       needed and summarized below.

   Records
       Normally, records are separated by newline characters.  You can control
       how records are separated by assigning values to the built-in variable
       RS.  If RS is any single character, that character separates records.
       Otherwise, RS is a regular expression.  Text in the input that matches
       this regular expression separates the record.  However, in
       compatibility mode, only the first character of its string value is
       used for separating records.  If RS is set to the null string, then
       records are separated by empty lines.  When RS is set to the null
       string, the newline character always acts as a field separator, in
       addition to whatever value FS may have.

   Fields
       As each input record is read, gawk splits the record into fields, using
       the value of the FS variable as the field separator.  If FS is a single
       character, fields are separated by that character.  If FS is the null
       string, then each individual character becomes a separate field.
       Otherwise, FS is expected to be a full regular expression.  In the
       special case that FS is a single space, fields are separated by runs of
       spaces and/or tabs and/or newlines.  NOTE: The value of IGNORECASE (see
       below) also affects how fields are split when FS is a regular
       expression, and how records are separated when RS is a regular
       expression.

       If the FIELDWIDTHS variable is set to a space-separated list of
       numbers, each field is expected to have fixed width, and gawk splits up
       the record using the specified widths.  Each field width may optionally
       be preceded by a colon-separated value specifying the number of
       characters to skip before the field starts.  The value of FS is
       ignored.  Assigning a new value to FS or FPAT overrides the use of
       FIELDWIDTHS.

       Similarly, if the FPAT variable is set to a string representing a
       regular expression, each field is made up of text that matches that
       regular expression. In this case, the regular expression describes the
       fields themselves, instead of the text that separates the fields.
       Assigning a new value to FS or FIELDWIDTHS overrides the use of FPAT.

       Each field in the input record may be referenced by its position: $1,
       $2, and so on.  $0 is the whole record.  Fields need not be referenced
       by constants:

              n = 5
              print $n

       prints the fifth field in the input record.

       The variable NF is set to the total number of fields in the input
       record.

       References to non-existent fields (i.e., fields after $NF) produce the
       null-string.  However, assigning to a non-existent field (e.g., $(NF+2)
       = 5) increases the value of NF, creates any intervening fields with the
       null string as their values, and causes the value of $0 to be
       recomputed, with the fields being separated by the value of OFS.
       References to negative numbered fields cause a fatal error.
       Decrementing NF causes the values of fields past the new value to be
       lost, and the value of $0 to be recomputed, with the fields being
       separated by the value of OFS.

       Assigning a value to an existing field causes the whole record to be
       rebuilt when $0 is referenced.  Similarly, assigning a value to $0
       causes the record to be resplit, creating new values for the fields.

   Built-in Variables
       Gawk's built-in variables are:

       ARGC        The number of command line arguments (does not include
                   options to gawk, or the program source).

       ARGIND      The index in ARGV of the current file being processed.

       ARGV        Array of command line arguments.  The array is indexed from
                   0 to ARGC - 1.  Dynamically changing the contents of ARGV
                   can control the files used for data.

       BINMODE     On non-POSIX systems, specifies use of “binary” mode for
                   all file I/O.  Numeric values of 1, 2, or 3, specify that
                   input files, output files, or all files, respectively,
                   should use binary I/O.  String values of "r", or "w"
                   specify that input files, or output files, respectively,
                   should use binary I/O.  String values of "rw" or "wr"
                   specify that all files should use binary I/O.  Any other
                   string value is treated as "rw", but generates a warning
                   message.

       CONVFMT     The conversion format for numbers, "%.6g", by default.

       ENVIRON     An array containing the values of the current environment.
                   The array is indexed by the environment variables, each
                   element being the value of that variable (e.g.,
                   ENVIRON["HOME"] might be "/home/arnold").

                   In POSIX mode, changing this array does not affect the
                   environment seen by programs which gawk spawns via
                   redirection or the system() function.  Otherwise, gawk
                   updates its real environment so that programs it spawns see
                   the changes.

       ERRNO       If a system error occurs either doing a redirection for
                   getline, during a read for getline, or during a close(),
                   then ERRNO is set to a string describing the error.  The
                   value is subject to translation in non-English locales.  If
                   the string in ERRNO corresponds to a system error in the
                   errno(3) variable, then the numeric value can be found in
                   PROCINFO["errno"].  For non-system errors,
                   PROCINFO["errno"] will be zero.

       FIELDWIDTHS A whitespace-separated list of field widths.  When set,
                   gawk parses the input into fields of fixed width, instead
                   of using the value of the FS variable as the field
                   separator.  Each field width may optionally be preceded by
                   a colon-separated value specifying the number of characters
                   to skip before the field starts.  See Fields, above.

       FILENAME    The name of the current input file.  If no files are
                   specified on the command line, the value of FILENAME is
                   “-”.  However, FILENAME is undefined inside the BEGIN rule
                   (unless set by getline).

       FNR         The input record number in the current input file.

       FPAT        A regular expression describing the contents of the fields
                   in a record.  When set, gawk parses the input into fields,
                   where the fields match the regular expression, instead of
                   using the value of the FS variable as the field separator.
                   See Fields, above.

       FS          The input field separator, a space by default.  See Fields,
                   above.

       FUNCTAB     An array whose indices and corresponding values are the
                   names of all the user-defined or extension functions in the
                   program.  NOTE: You may not use the delete statement with
                   the FUNCTAB array.

       IGNORECASE  Controls the case-sensitivity of all regular expression and
                   string operations.  If IGNORECASE has a non-zero value,
                   then string comparisons and pattern matching in rules,
                   field splitting with FS and FPAT, record separating with
                   RS, regular expression matching with ~ and !~, and the
                   gensub(), gsub(), index(), match(), patsplit(), split(),
                   and sub() built-in functions all ignore case when doing
                   regular expression operations.  NOTE: Array subscripting is
                   not affected.  However, the asort() and asorti() functions
                   are affected.
                   Thus, if IGNORECASE is not equal to zero, /aB/ matches all
                   of the strings "ab", "aB", "Ab", and "AB".  As with all AWK
                   variables, the initial value of IGNORECASE is zero, so all
                   regular expression and string operations are normally case-
                   sensitive.

       LINT        Provides dynamic control of the --lint option from within
                   an AWK program.  When true, gawk prints lint warnings. When
                   false, it does not.  When assigned the string value
                   "fatal", lint warnings become fatal errors, exactly like
                   --lint=fatal.  Any other true value just prints warnings.

       NF          The number of fields in the current input record.

       NR          The total number of input records seen so far.

       OFMT        The output format for numbers, "%.6g", by default.

       OFS         The output field separator, a space by default.

       ORS         The output record separator, by default a newline.

       PREC        The working precision of arbitrary precision floating-point
                   numbers, 53 by default.

       PROCINFO    The elements of this array provide access to information
                   about the running AWK program.  On some systems, there may
                   be elements in the array, "group1" through "groupn" for
                   some n, which is the number of supplementary groups that
                   the process has.  Use the in operator to test for these
                   elements.  The following elements are guaranteed to be
                   available:

                   PROCINFO["argv"]     The command line arguments as received
                                        by gawk at the C-language level.  The
                                        subscripts start from zero.

                   PROCINFO["egid"]     The value of the getegid(2) system
                                        call.

                   PROCINFO["errno"]    The value of errno(3) when ERRNO is
                                        set to the associated error message.

                   PROCINFO["euid"]     The value of the geteuid(2) system
                                        call.

                   PROCINFO["FS"]       "FS" if field splitting with FS is in
                                        effect, "FPAT" if field splitting with
                                        FPAT is in effect, "FIELDWIDTHS" if
                                        field splitting with FIELDWIDTHS is in
                                        effect, or "API" if API input parser
                                        field splitting is in effect.

                   PROCINFO["gid"]      The value of the getgid(2) system
                                        call.

                   PROCINFO["identifiers"]
                                        A subarray, indexed by the names of
                                        all identifiers used in the text of
                                        the AWK program.  The values indicate
                                        what gawk knows about the identifiers
                                        after it has finished parsing the
                                        program; they are not updated while
                                        the program runs.  For each
                                        identifier, the value of the element
                                        is one of the following:

                                        "array"     The identifier is an
                                                    array.

                                        "builtin"   The identifier is a built-
                                                    in function.

                                        "extension" The identifier is an
                                                    extension function loaded
                                                    via @load or -l.

                                        "scalar"    The identifier is a
                                                    scalar.

                                        "untyped"   The identifier is untyped
                                                    (could be used as a scalar
                                                    or array, gawk doesn't
                                                    know yet).

                                        "user"      The identifier is a user-
                                                    defined function.

                   PROCINFO["pgrpid"]   The process group ID of the current
                                        process.

                   PROCINFO["pid"]      The process ID of the current process.

                   PROCINFO["ppid"]     The parent process ID of the current
                                        process.

                   PROCINFO["strftime"] The default time format string for
                                        strftime().

                   PROCINFO["uid"]      The value of the getuid(2) system
                                        call.

                   PROCINFO["version"]  the version of gawk.

                   The following elements are present if loading dynamic
                   extensions is available:

                   PROCINFO["api_major"]
                          The major version of the extension API.

                   PROCINFO["api_minor"]
                          The minor version of the extension API.

                   The following elements are available if MPFR support is
                   compiled into gawk:

                   PROCINFO["gmp_version"]
                          The version of the GNU MP library used for arbitrary
                          precision number support in gawk.

                   PROCINFO["mpfr_version"]
                          The version of the GNU MPFR library used for
                          arbitrary precision number support in gawk.

                   PROCINFO["prec_max"]
                          The maximum precision supported by the GNU MPFR
                          library for arbitrary precision floating-point
                          numbers.

                   PROCINFO["prec_min"]
                          The minimum precision allowed by the GNU MPFR
                          library for arbitrary precision floating-point
                          numbers.

                   The following elements may set by a program to change
                   gawk's behavior:

                   PROCINFO["NONFATAL"]
                          If this exists, then I/O errors for all redirections
                          become nonfatal.

                   PROCINFO["ame", "NONFATAL"]
                          Make I/O errors for name be nonfatal.

                   PROCINFO["command", "pty"]
                          Use a pseudo-tty for two-way communication with
                          command instead of setting up two one-way pipes.

                   PROCINFO["input", "READ_TIMEOUT"]
                          The timeout in milliseconds for reading data from
                          input, where input is a redirection string or a
                          filename. A value of zero or less than zero means no
                          timeout.

                   PROCINFO["input", "RETRY"]
                          If an I/O error that may be retried occurs when
                          reading data from input, and this array entry
                          exists, then getline returns -2 instead of following
                          the default behavior of returning -1 and configuring
                          input to return no further data.  An I/O error that
                          may be retried is one where errno(3) has the value
                          EAGAIN, EWOULDBLOCK, EINTR, or ETIMEDOUT.  This may
                          be useful in conjunction with PROCINFO["input",
                          "READ_TIMEOUT"] or situations where a file
                          descriptor has been configured to behave in a non-
                          blocking fashion.

                   PROCINFO["sorted_in"]
                          If this element exists in PROCINFO, then its value
                          controls the order in which array elements are
                          traversed in for loops.  Supported values are
                          "@ind_str_asc", "@ind_num_asc", "@val_type_asc",
                          "@val_str_asc", "@val_num_asc", "@ind_str_desc",
                          "@ind_num_desc", "@val_type_desc", "@val_str_desc",
                          "@val_num_desc", and "@unsorted".  The value can
                          also be the name (as a string) of any comparison
                          function defined as follows:

                               function cmp_func(i1, v1, i2, v2)

                          where i1 and i2 are the indices, and v1 and v2 are
                          the corresponding values of the two elements being
                          compared.  It should return a number less than,
                          equal to, or greater than 0, depending on how the
                          elements of the array are to be ordered.

       ROUNDMODE   The rounding mode to use for arbitrary precision arithmetic
                   on numbers, by default "N" (IEEE-754 roundTiesToEven mode).
                   The accepted values are "N" or "n" for roundTiesToEven, "U"
                   or "u" for roundTowardPositive, "D" or "d" for
                   roundTowardNegative, "Z" or "z" for roundTowardZero, and if
                   your version of GNU MPFR library supports it, "A" or "a"
                   for rounding away from zero.

       RS          The input record separator, by default a newline.

       RT          The record terminator.  Gawk sets RT to the input text that
                   matched the character or regular expression specified by
                   RS.

       RSTART      The index of the first character matched by match(); 0 if
                   no match.  (This implies that character indices start at
                   one.)

       RLENGTH     The length of the string matched by match(); -1 if no
                   match.

       SUBSEP      The character used to separate multiple subscripts in array
                   elements, by default "\034".

       SYMTAB      An array whose indices are the names of all currently
                   defined global variables and arrays in the program.  The
                   array may be used for indirect access to read or write the
                   value of a variable:

                        foo = 5
                        SYMTAB["foo"] = 4
                        print foo    # prints 4

                   The typeof() function may be used to test if an element in
                   SYMTAB is an array.  You may not use the delete statement
                   with the SYMTAB array.

       TEXTDOMAIN  The text domain of the AWK program; used to find the
                   localized translations for the program's strings.

   Arrays
       Arrays are subscripted with an expression between square brackets ([
       and ]).  If the expression is an expression list (expr, expr ...)  then
       the array subscript is a string consisting of the concatenation of the
       (string) value of each expression, separated by the value of the SUBSEP
       variable.  This facility is used to simulate multiply dimensioned
       arrays.  For example:

              i = "A"; j = "B"; k = "C"
              x[i, j, k] = "hello, world\n"

       assigns the string "hello, world\n" to the element of the array x which
       is indexed by the string "A\034B\034C".  All arrays in AWK are
       associative, i.e., indexed by string values.

       The special operator in may be used to test if an array has an index
       consisting of a particular value:

              if (val in array)
                   print array[val]

       If the array has multiple subscripts, use (i, j) in array.

       The in construct may also be used in a for loop to iterate over all the
       elements of an array.  However, the (i, j) in array construct only
       works in tests, not in for loops.

       An element may be deleted from an array using the delete statement.
       The delete statement may also be used to delete the entire contents of
       an array, just by specifying the array name without a subscript.

       gawk supports true multidimensional arrays. It does not require that
       such arrays be ``rectangular'' as in C or C++.  For example:

              a[1] = 5
              a[2][1] = 6
              a[2][2] = 7

       NOTE: You may need to tell gawk that an array element is really a
       subarray in order to use it where gawk expects an array (such as in the
       second argument to split()).  You can do this by creating an element in
       the subarray and then deleting it with the delete statement.

   Variable Typing And Conversion
       Variables and fields may be (floating point) numbers, or strings, or
       both.  They may also be regular expressions. How the value of a
       variable is interpreted depends upon its context.  If used in a numeric
       expression, it will be treated as a number; if used as a string it will
       be treated as a string.

       To force a variable to be treated as a number, add zero to it; to force
       it to be treated as a string, concatenate it with the null string.

       Uninitialized variables have the numeric value zero and the string
       value "" (the null, or empty, string).

       When a string must be converted to a number, the conversion is
       accomplished using strtod(3).  A number is converted to a string by
       using the value of CONVFMT as a format string for sprintf(3), with the
       numeric value of the variable as the argument.  However, even though
       all numbers in AWK are floating-point, integral values are always
       converted as integers.  Thus, given

              CONVFMT = "%2.2f"
              a = 12
              b = a ""

       the variable b has a string value of "12" and not "12.00".

       NOTE: When operating in POSIX mode (such as with the --posix option),
       beware that locale settings may interfere with the way decimal numbers
       are treated: the decimal separator of the numbers you are feeding to
       gawk must conform to what your locale would expect, be it a comma (,)
       or a period (.).

       Gawk performs comparisons as follows: If two variables are numeric,
       they are compared numerically.  If one value is numeric and the other
       has a string value that is a “numeric string,” then comparisons are
       also done numerically.  Otherwise, the numeric value is converted to a
       string and a string comparison is performed.  Two strings are compared,
       of course, as strings.

       Note that string constants, such as "57", are not numeric strings, they
       are string constants.  The idea of “numeric string” only applies to
       fields, getline input, FILENAME, ARGV elements, ENVIRON elements and
       the elements of an array created by split() or patsplit() that are
       numeric strings.  The basic idea is that user input, and only user
       input, that looks numeric, should be treated that way.

   Octal and Hexadecimal Constants
       You may use C-style octal and hexadecimal constants in your AWK program
       source code.  For example, the octal value 011 is equal to decimal 9,
       and the hexadecimal value 0x11 is equal to decimal 17.

   String Constants
       String constants in AWK are sequences of characters enclosed between
       double quotes (like "value").  Within strings, certain escape sequences
       are recognized, as in C.  These are:

       \\   A literal backslash.

       \a   The “alert” character; usually the ASCII BEL character.

       \b   Backspace.

       \f   Form-feed.

       \n   Newline.

       \r   Carriage return.

       \t   Horizontal tab.

       \v   Vertical tab.

       \xhex digits
            The character represented by the string of hexadecimal digits
            following the \x.  Up to two following hexadecimal digits are
            considered part of the escape sequence.  E.g., "\x1B" is the ASCII
            ESC (escape) character.

       \ddd The character represented by the 1-, 2-, or 3-digit sequence of
            octal digits.  E.g., "\033" is the ASCII ESC (escape) character.

       \c   The literal character c.

       In compatibility mode, the characters represented by octal and
       hexadecimal escape sequences are treated literally when used in regular
       expression constants.  Thus, /a\52b/ is equivalent to /a\*b/.

   Regexp Constants
       A regular expression constant is a sequence of characters enclosed
       between forward slashes (like /value/).  Regular expression matching is
       described more fully below; see Regular Expressions.

       The escape sequences described earlier may also be used inside constant
       regular expressions (e.g., /[ \t\f\n\r\v]/ matches whitespace
       characters).

       Gawk   provides strongly typed regular expression constants. These are
              written with a leading @ symbol (like so: @/value/).  Such
              constants may be assigned to scalars (variables, array elements)
              and passed to user-defined functions. Variables that have been
              so assigned have regular expression type.

PATTERNS AND ACTIONS
       AWK is a line-oriented language.  The pattern comes first, and then the
       action.  Action statements are enclosed in { and }.  Either the pattern
       may be missing, or the action may be missing, but, of course, not both.
       If the pattern is missing, the action executes for every single record
       of input.  A missing action is equivalent to

              { print }

       which prints the entire record.

       Comments begin with the # character, and continue until the end of the
       line.  Empty lines may be used to separate statements.  Normally, a
       statement ends with a newline, however, this is not the case for lines
       ending in a comma, {, ?, :, &&, or ||.  Lines ending in do or else also
       have their statements automatically continued on the following line.
       In other cases, a line can be continued by ending it with a “\”, in
       which case the newline is ignored.

       Multiple statements may be put on one line by separating them with a
       “;”.  This applies to both the statements within the action part of a
       pattern-action pair (the usual case), and to the pattern-action
       statements themselves.

   Patterns
       AWK patterns may be one of the following:

              BEGIN
              END
              BEGINFILE
              ENDFILE
              /regular expression/
              relational expression
              pattern && pattern
              pattern || pattern
              pattern ? pattern : pattern
              (pattern)
              ! pattern
              pattern1, pattern2

       BEGIN and END are two special kinds of patterns which are not tested
       against the input.  The action parts of all BEGIN patterns are merged
       as if all the statements had been written in a single BEGIN rule.  They
       are executed before any of the input is read.  Similarly, all the END
       rules are merged, and executed when all the input is exhausted (or when
       an exit statement is executed).  BEGIN and END patterns cannot be
       combined with other patterns in pattern expressions.  BEGIN and END
       patterns cannot have missing action parts.

       BEGINFILE and ENDFILE are additional special patterns whose bodies are
       executed before reading the first record of each command line input
       file and after reading the last record of each file.  Inside the
       BEGINFILE rule, the value of ERRNO is the empty string if the file was
       opened successfully.  Otherwise, there is some problem with the file
       and the code should use nextfile to skip it. If that is not done, gawk
       produces its usual fatal error for files that cannot be opened.

       For /regular expression/ patterns, the associated statement is executed
       for each input record that matches the regular expression.  Regular
       expressions are the same as those in egrep(1), and are summarized
       below.

       A relational expression may use any of the operators defined below in
       the section on actions.  These generally test whether certain fields
       match certain regular expressions.

       The &&, ||, and !  operators are logical AND, logical OR, and logical
       NOT, respectively, as in C.  They do short-circuit evaluation, also as
       in C, and are used for combining more primitive pattern expressions.
       As in most languages, parentheses may be used to change the order of
       evaluation.

       The ?: operator is like the same operator in C.  If the first pattern
       is true then the pattern used for testing is the second pattern,
       otherwise it is the third.  Only one of the second and third patterns
       is evaluated.

       The pattern1, pattern2 form of an expression is called a range pattern.
       It matches all input records starting with a record that matches
       pattern1, and continuing until a record that matches pattern2,
       inclusive.  It does not combine with any other sort of pattern
       expression.

   Regular Expressions
       Regular expressions are the extended kind found in egrep.  They are
       composed of characters as follows:

       c          Matches the non-metacharacter c.

       \c         Matches the literal character c.

       .          Matches any character including newline.

       ^          Matches the beginning of a string.

       $          Matches the end of a string.

       [abc...]   A character list: matches any of the characters abc....  You
                  may include a range of characters by separating them with a
                  dash.

       [^abc...]  A negated character list: matches any character except
                  abc....

       r1|r2      Alternation: matches either r1 or r2.

       r1r2       Concatenation: matches r1, and then r2.

       r+         Matches one or more r's.

       r*         Matches zero or more r's.

       r?         Matches zero or one r's.

       (r)        Grouping: matches r.

       r{n}
       r{n,}
       r{n,m}     One or two numbers inside braces denote an interval
                  expression.  If there is one number in the braces, the
                  preceding regular expression r is repeated n times.  If
                  there are two numbers separated by a comma, r is repeated n
                  to m times.  If there is one number followed by a comma,
                  then r is repeated at least n times.

       \y         Matches the empty string at either the beginning or the end
                  of a word.

       \B         Matches the empty string within a word.

       \<         Matches the empty string at the beginning of a word.

       \>         Matches the empty string at the end of a word.

       \s         Matches any whitespace character.

       \S         Matches any nonwhitespace character.

       \w         Matches any word-constituent character (letter, digit, or
                  underscore).

       \W         Matches any character that is not word-constituent.

       \`         Matches the empty string at the beginning of a buffer
                  (string).

       \'         Matches the empty string at the end of a buffer.

       The escape sequences that are valid in string constants (see String
       Constants) are also valid in regular expressions.

       Character classes are a feature introduced in the POSIX standard.  A
       character class is a special notation for describing lists of
       characters that have a specific attribute, but where the actual
       characters themselves can vary from country to country and/or from
       character set to character set.  For example, the notion of what is an
       alphabetic character differs in the USA and in France.

       A character class is only valid in a regular expression inside the
       brackets of a character list.  Character classes consist of [:, a
       keyword denoting the class, and :].  The character classes defined by
       the POSIX standard are:

       [:alnum:]  Alphanumeric characters.

       [:alpha:]  Alphabetic characters.

       [:blank:]  Space or tab characters.

       [:cntrl:]  Control characters.

       [:digit:]  Numeric characters.

       [:graph:]  Characters that are both printable and visible.  (A space is
                  printable, but not visible, while an a is both.)

       [:lower:]  Lowercase alphabetic characters.

       [:print:]  Printable characters (characters that are not control
                  characters.)

       [:punct:]  Punctuation characters (characters that are not letter,
                  digits, control characters, or space characters).

       [:space:]  Space characters (such as space, tab, and formfeed, to name
                  a few).

       [:upper:]  Uppercase alphabetic characters.

       [:xdigit:] Characters that are hexadecimal digits.

       For example, before the POSIX standard, to match alphanumeric
       characters, you would have had to write /[A-Za-z0-9]/.  If your
       character set had other alphabetic characters in it, this would not
       match them, and if your character set collated differently from ASCII,
       this might not even match the ASCII alphanumeric characters.  With the
       POSIX character classes, you can write /[[:alnum:]]/, and this matches
       the alphabetic and numeric characters in your character set, no matter
       what it is.

       Two additional special sequences can appear in character lists.  These
       apply to non-ASCII character sets, which can have single symbols
       (called collating elements) that are represented with more than one
       character, as well as several characters that are equivalent for
       collating, or sorting, purposes.  (E.g., in French, a plain “e” and a
       grave-accented “`” are equivalent.)

       Collating Symbols
              A collating symbol is a multi-character collating element
              enclosed in [.  and .].  For example, if ch is a collating
              element, then [[.ch.]]  is a regular expression that matches
              this collating element, while [ch] is a regular expression that
              matches either c or h.

       Equivalence Classes
              An equivalence class is a locale-specific name for a list of
              characters that are equivalent.  The name is enclosed in [= and
              =].  For example, the name e might be used to represent all of
              “e”, “´”, and “`”.  In this case, [[=e=]] is a regular
              expression that matches any of e, ´, or `.

       These features are very valuable in non-English speaking locales.  The
       library functions that gawk uses for regular expression matching
       currently only recognize POSIX character classes; they do not recognize
       collating symbols or equivalence classes.

       The \y, \B, \<, \>, \s, \S, \w, \W, \`, and \' operators are specific
       to gawk; they are extensions based on facilities in the GNU regular
       expression libraries.

       The various command line options control how gawk interprets characters
       in regular expressions.

       No options
              In the default case, gawk provides all the facilities of POSIX
              regular expressions and the GNU regular expression operators
              described above.

       --posix
              Only POSIX regular expressions are supported, the GNU operators
              are not special.  (E.g., \w matches a literal w).

       --traditional
              Traditional UNIX awk regular expressions are matched.  The GNU
              operators are not special, and interval expressions are not
              available.  Characters described by octal and hexadecimal escape
              sequences are treated literally, even if they represent regular
              expression metacharacters.

       --re-interval
              Allow interval expressions in regular expressions, even if
              --traditional has been provided.

   Actions
       Action statements are enclosed in braces, { and }.  Action statements
       consist of the usual assignment, conditional, and looping statements
       found in most languages.  The operators, control statements, and
       input/output statements available are patterned after those in C.

   Operators
       The operators in AWK, in order of decreasing precedence, are:

       (...)       Grouping

       $           Field reference.

       ++ --       Increment and decrement, both prefix and postfix.

       ^           Exponentiation (** may also be used, and **= for the
                   assignment operator).

       + - !       Unary plus, unary minus, and logical negation.

       * / %       Multiplication, division, and modulus.

       + -         Addition and subtraction.

       space       String concatenation.

       |   |&      Piped I/O for getline, print, and printf.

       < > <= >= == !=
                   The regular relational operators.

       ~ !~        Regular expression match, negated match.  NOTE: Do not use
                   a constant regular expression (/foo/) on the left-hand side
                   of a ~ or !~.  Only use one on the right-hand side.  The
                   expression /foo/ ~ exp has the same meaning as (($0 ~
                   /foo/) ~ exp).  This is usually not what you want.

       in          Array membership.

       &&          Logical AND.

       ||          Logical OR.

       ?:          The C conditional expression.  This has the form expr1 ?
                   expr2 : expr3.  If expr1 is true, the value of the
                   expression is expr2, otherwise it is expr3.  Only one of
                   expr2 and expr3 is evaluated.

       = += -= *= /= %= ^=
                   Assignment.  Both absolute assignment (var = value) and
                   operator-assignment (the other forms) are supported.

   Control Statements
       The control statements are as follows:

              if (condition) statement [ else statement ]
              while (condition) statement
              do statement while (condition)
              for (expr1; expr2; expr3) statement
              for (var in array) statement
              break
              continue
              delete array[index]
              delete array
              exit [ expression ]
              { statements }
              switch (expression) {
              case value|regex : statement
              ...
              [ default: statement ]
              }

   I/O Statements
       The input/output statements are as follows:

       close(file [, how])   Close file, pipe or coprocess.  The optional how
                             should only be used when closing one end of a
                             two-way pipe to a coprocess.  It must be a string
                             value, either "to" or "from".

       getline               Set $0 from next input record; set NF, NR, FNR,
                             RT.

       getline <file         Set $0 from next record of file; set NF, RT.

       getline var           Set var from next input record; set NR, FNR, RT.

       getline var <file     Set var from next record of file, RT.

       command | getline [var]
                             Run command piping the output either into $0 or
                             var, as above, and RT.

       command |& getline [var]
                             Run command as a coprocess piping the output
                             either into $0 or var, as above, and RT.
                             Coprocesses are a gawk extension.  (command can
                             also be a socket.  See the subsection Special
                             File Names, below.)

       next                  Stop processing the current input record.  The
                             next input record is read and processing starts
                             over with the first pattern in the AWK program.
                             Upon reaching the end of the input data, gawk
                             executes any END rule(s).

       nextfile              Stop processing the current input file.  The next
                             input record read comes from the next input file.
                             FILENAME and ARGIND are updated, FNR is reset to
                             1, and processing starts over with the first
                             pattern in the AWK program.  Upon reaching the
                             end of the input data, gawk executes any ENDFILE
                             and END rule(s).

       print                 Print the current record.  The output record is
                             terminated with the value of ORS.

       print expr-list       Print expressions.  Each expression is separated
                             by the value of OFS.  The output record is
                             terminated with the value of ORS.

       print expr-list >file Print expressions on file.  Each expression is
                             separated by the value of OFS.  The output record
                             is terminated with the value of ORS.

       printf fmt, expr-list Format and print.  See The printf Statement,
                             below.

       printf fmt, expr-list >file
                             Format and print on file.

       system(cmd-line)      Execute the command cmd-line, and return the exit
                             status.  (This may not be available on non-POSIX
                             systems.)  See GAWK: Effective AWK Programming
                             for the full details on the exit status.

       fflush([file])        Flush any buffers associated with the open output
                             file or pipe file.  If file is missing or if it
                             is the null string, then flush all open output
                             files and pipes.

       Additional output redirections are allowed for print and printf.

       print ... >> file
              Appends output to the file.

       print ... | command
              Writes on a pipe.

       print ... |& command
              Sends data to a coprocess or socket.  (See also the subsection
              Special File Names, below.)

       The getline command returns 1 on success, zero on end of file, and -1
       on an error.  If the errno(3) value indicates that the I/O operation
       may be retried, and PROCINFO["input", "RETRY"] is set, then -2 is
       returned instead of -1, and further calls to getline may be attempted.
       Upon an error, ERRNO is set to a string describing the problem.

       NOTE: Failure in opening a two-way socket results in a non-fatal error
       being returned to the calling function. If using a pipe, coprocess, or
       socket to getline, or from print or printf within a loop, you must use
       close() to create new instances of the command or socket.  AWK does not
       automatically close pipes, sockets, or coprocesses when they return
       EOF.

   The printf Statement
       The AWK versions of the printf statement and sprintf() function (see
       below) accept the following conversion specification formats:

       %c      A single character.  If the argument used for %c is numeric, it
               is treated as a character and printed.  Otherwise, the argument
               is assumed to be a string, and the only first character of that
               string is printed.

       %d, %i  A decimal number (the integer part).

       %e, %E  A floating point number of the form [-]d.dddddde[+-]dd.  The %E
               format uses E instead of e.

       %f, %F  A floating point number of the form [-]ddd.dddddd.  If the
               system library supports it, %F is available as well. This is
               like %f, but uses capital letters for special “not a number”
               and “infinity” values. If %F is not available, gawk uses %f.

       %g, %G  Use %e or %f conversion, whichever is shorter, with
               nonsignificant zeros suppressed.  The %G format uses %E instead
               of %e.

       %o      An unsigned octal number (also an integer).

       %u      An unsigned decimal number (again, an integer).

       %s      A character string.

       %x, %X  An unsigned hexadecimal number (an integer).  The %X format
               uses ABCDEF instead of abcdef.

       %%      A single % character; no argument is converted.

       Optional, additional parameters may lie between the % and the control
       letter:

       count$ Use the count'th argument at this point in the formatting.  This
              is called a positional specifier and is intended primarily for
              use in translated versions of format strings, not in the
              original text of an AWK program.  It is a gawk extension.

       -      The expression should be left-justified within its field.

       space  For numeric conversions, prefix positive values with a space,
              and negative values with a minus sign.

       +      The plus sign, used before the width modifier (see below), says
              to always supply a sign for numeric conversions, even if the
              data to be formatted is positive.  The + overrides the space
              modifier.

       #      Use an “alternate form” for certain control letters.  For %o,
              supply a leading zero.  For %x, and %X, supply a leading 0x or
              0X for a nonzero result.  For %e, %E, %f and %F, the result
              always contains a decimal point.  For %g, and %G, trailing zeros
              are not removed from the result.

       0      A leading 0 (zero) acts as a flag, indicating that output should
              be padded with zeroes instead of spaces.  This applies only to
              the numeric output formats.  This flag only has an effect when
              the field width is wider than the value to be printed.

       '      A single quote character instructs gawk to insert the locale's
              thousands-separator character into decimal numbers, and to also
              use the locale's decimal point character with floating point
              formats.  This requires correct locale support in the C library
              and in the definition of the current locale.

       width  The field should be padded to this width.  The field is normally
              padded with spaces.  With the 0 flag, it is padded with zeroes.

       .prec  A number that specifies the precision to use when printing.  For
              the %e, %E, %f and %F, formats, this specifies the number of
              digits you want printed to the right of the decimal point.  For
              the %g, and %G formats, it specifies the maximum number of
              significant digits.  For the %d, %i, %o, %u, %x, and %X formats,
              it specifies the minimum number of digits to print.  For %s, it
              specifies the maximum number of characters from the string that
              should be printed.

       The dynamic width and prec capabilities of the ISO C printf() routines
       are supported.  A * in place of either the width or prec specifications
       causes their values to be taken from the argument list to printf or
       sprintf().  To use a positional specifier with a dynamic width or
       precision, supply the count$ after the * in the format string.  For
       example, "%3$*2$.*1$s".

   Special File Names
       When doing I/O redirection from either print or printf into a file, or
       via getline from a file, gawk recognizes certain special filenames
       internally.  These filenames allow access to open file descriptors
       inherited from gawk's parent process (usually the shell).  These file
       names may also be used on the command line to name data files.  The
       filenames are:

       -           The standard input.

       /dev/stdin  The standard input.

       /dev/stdout The standard output.

       /dev/stderr The standard error output.

       /dev/fd/n   The file associated with the open file descriptor n.

       These are particularly useful for error messages.  For example:

              print "You blew it!" > "/dev/stderr"

       whereas you would otherwise have to use

              print "You blew it!" | "cat 1>&2"

       The following special filenames may be used with the |& coprocess
       operator for creating TCP/IP network connections:

       /inet/tcp/lport/rhost/rport
       /inet4/tcp/lport/rhost/rport
       /inet6/tcp/lport/rhost/rport
              Files for a TCP/IP connection on local port lport to remote host
              rhost on remote port rport.  Use a port of 0 to have the system
              pick a port.  Use /inet4 to force an IPv4 connection, and /inet6
              to force an IPv6 connection.  Plain /inet uses the system
              default (most likely IPv4).

       /inet/udp/lport/rhost/rport
       /inet4/udp/lport/rhost/rport
       /inet6/udp/lport/rhost/rport
              Similar, but use UDP/IP instead of TCP/IP.

   Numeric Functions
       AWK has the following built-in arithmetic functions:

       atan2(y, x)   Return the arctangent of y/x in radians.

       cos(expr)     Return the cosine of expr, which is in radians.

       exp(expr)     The exponential function.

       int(expr)     Truncate to integer.

       log(expr)     The natural logarithm function.

       rand()        Return a random number N, between zero and one, such that
                     0 ≤ N < 1.

       sin(expr)     Return the sine of expr, which is in radians.

       sqrt(expr)    Return the square root of expr.

       srand([expr]) Use expr as the new seed for the random number generator.
                     If no expr is provided, use the time of day.  Return the
                     previous seed for the random number generator.

   String Functions
       Gawk has the following built-in string functions:

       asort(s [, d [, how] ]) Return the number of elements in the source
                               array s.  Sort the contents of s using gawk's
                               normal rules for comparing values, and replace
                               the indices of the sorted values s with
                               sequential integers starting with 1. If the
                               optional destination array d is specified,
                               first duplicate s into d, and then sort d,
                               leaving the indices of the source array s
                               unchanged. The optional string how controls the
                               direction and the comparison mode.  Valid
                               values for how are any of the strings valid for
                               PROCINFO["sorted_in"].  It can also be the name
                               of a user-defined comparison function as
                               described in PROCINFO["sorted_in"].

       asorti(s [, d [, how] ])
                               Return the number of elements in the source
                               array s.  The behavior is the same as that of
                               asort(), except that the array indices are used
                               for sorting, not the array values.  When done,
                               the array is indexed numerically, and the
                               values are those of the original indices.  The
                               original values are lost; thus provide a second
                               array if you wish to preserve the original.
                               The purpose of the optional string how is the
                               same as described previously for asort().

       gensub(r, s, h [, t])   Search the target string t for matches of the
                               regular expression r.  If h is a string
                               beginning with g or G, then replace all matches
                               of r with s.  Otherwise, h is a number
                               indicating which match of r to replace.  If t
                               is not supplied, use $0 instead.  Within the
                               replacement text s, the sequence \n, where n is
                               a digit from 1 to 9, may be used to indicate
                               just the text that matched the n'th
                               parenthesized subexpression.  The sequence \0
                               represents the entire matched text, as does the
                               character &.  Unlike sub() and gsub(), the
                               modified string is returned as the result of
                               the function, and the original target string is
                               not changed.

       gsub(r, s [, t])        For each substring matching the regular
                               expression r in the string t, substitute the
                               string s, and return the number of
                               substitutions.  If t is not supplied, use $0.
                               An & in the replacement text is replaced with
                               the text that was actually matched.  Use \& to
                               get a literal &.  (This must be typed as "\\&";
                               see GAWK: Effective AWK Programming for a
                               fuller discussion of the rules for ampersands
                               and backslashes in the replacement text of
                               sub(), gsub(), and gensub().)

       index(s, t)             Return the index of the string t in the string
                               s, or zero if t is not present.  (This implies
                               that character indices start at one.)  It is a
                               fatal error to use a regexp constant for t.

       length([s])             Return the length of the string s, or the
                               length of $0 if s is not supplied.  As a non-
                               standard extension, with an array argument,
                               length() returns the number of elements in the
                               array.

       match(s, r [, a])       Return the position in s where the regular
                               expression r occurs, or zero if r is not
                               present, and set the values of RSTART and
                               RLENGTH.  Note that the argument order is the
                               same as for the ~ operator: str ~ re.  If array
                               a is provided, a is cleared and then elements 1
                               through n are filled with the portions of s
                               that match the corresponding parenthesized
                               subexpression in r.  The zero'th element of a
                               contains the portion of s matched by the entire
                               regular expression r.  Subscripts a[n,
                               "start"], and a[n, "length"] provide the
                               starting index in the string and length
                               respectively, of each matching substring.

       patsplit(s, a [, r [, seps] ])
                               Split the string s into the array a and the
                               separators array seps on the regular expression
                               r, and return the number of fields.  Element
                               values are the portions of s that matched r.
                               The value of seps[i] is the possibly null
                               separator that appeared after a[i].  The value
                               of seps[0] is the possibly null leading
                               separator.  If r is omitted, FPAT is used
                               instead.  The arrays a and seps are cleared
                               first.  Splitting behaves identically to field
                               splitting with FPAT, described above.

       split(s, a [, r [, seps] ])
                               Split the string s into the array a and the
                               separators array seps on the regular expression
                               r, and return the number of fields.  If r is
                               omitted, FS is used instead.  The arrays a and
                               seps are cleared first.  seps[i] is the field
                               separator matched by r between a[i] and a[i+1].
                               If r is a single space, then leading whitespace
                               in s goes into the extra array element seps[0]
                               and trailing whitespace goes into the extra
                               array element seps[n], where n is the return
                               value of split(s, a, r, seps).  Splitting
                               behaves identically to field splitting,
                               described above.

       sprintf(fmt, expr-list) Print expr-list according to fmt, and return
                               the resulting string.

       strtonum(str)           Examine str, and return its numeric value.  If
                               str begins with a leading 0, treat it as an
                               octal number.  If str begins with a leading 0x
                               or 0X, treat it as a hexadecimal number.
                               Otherwise, assume it is a decimal number.

       sub(r, s [, t])         Just like gsub(), but replace only the first
                               matching substring.  Return either zero or one.

       substr(s, i [, n])      Return the at most n-character substring of s
                               starting at i.  If n is omitted, use the rest
                               of s.

       tolower(str)            Return a copy of the string str, with all the
                               uppercase characters in str translated to their
                               corresponding lowercase counterparts.  Non-
                               alphabetic characters are left unchanged.

       toupper(str)            Return a copy of the string str, with all the
                               lowercase characters in str translated to their
                               corresponding uppercase counterparts.  Non-
                               alphabetic characters are left unchanged.

       Gawk is multibyte aware.  This means that index(), length(), substr()
       and match() all work in terms of characters, not bytes.

   Time Functions
       Since one of the primary uses of AWK programs is processing log files
       that contain time stamp information, gawk provides the following
       functions for obtaining time stamps and formatting them.

       mktime(datespec [, utc-flag])
                 Turn datespec into a time stamp of the same form as returned
                 by systime(), and return the result.  The datespec is a
                 string of the form YYYY MM DD HH MM SS[ DST].  The contents
                 of the string are six or seven numbers representing
                 respectively the full year including century, the month from
                 1 to 12, the day of the month from 1 to 31, the hour of the
                 day from 0 to 23, the minute from 0 to 59, the second from 0
                 to 60, and an optional daylight saving flag.  The values of
                 these numbers need not be within the ranges specified; for
                 example, an hour of -1 means 1 hour before midnight.  The
                 origin-zero Gregorian calendar is assumed, with year 0
                 preceding year 1 and year -1 preceding year 0.  If utc-flag
                 is present and is non-zero or non-null, the time is assumed
                 to be in the UTC time zone; otherwise, the time is assumed to
                 be in the local time zone.  If the DST daylight saving flag
                 is positive, the time is assumed to be daylight saving time;
                 if zero, the time is assumed to be standard time; and if
                 negative (the default), mktime() attempts to determine
                 whether daylight saving time is in effect for the specified
                 time.  If datespec does not contain enough elements or if the
                 resulting time is out of range, mktime() returns -1.

       strftime([format [, timestamp[, utc-flag]]])
                 Format timestamp according to the specification in format.
                 If utc-flag is present and is non-zero or non-null, the
                 result is in UTC, otherwise the result is in local time.  The
                 timestamp should be of the same form as returned by
                 systime().  If timestamp is missing, the current time of day
                 is used.  If format is missing, a default format equivalent
                 to the output of date(1) is used.  The default format is
                 available in PROCINFO["strftime"].  See the specification for
                 the strftime() function in ISO C for the format conversions
                 that are guaranteed to be available.

       systime() Return the current time of day as the number of seconds since
                 the Epoch (1970-01-01 00:00:00 UTC on POSIX systems).

   Bit Manipulations Functions
       Gawk supplies the following bit manipulation functions.  They work by
       converting double-precision floating point values to uintmax_t
       integers, doing the operation, and then converting the result back to
       floating point.

       NOTE: Passing negative operands to any of these functions causes a
       fatal error.

       The functions are:

       and(v1, v2 [, ...]) Return the bitwise AND of the values provided in
                           the argument list.  There must be at least two.

       compl(val)          Return the bitwise complement of val.

       lshift(val, count)  Return the value of val, shifted left by count
                           bits.

       or(v1, v2 [, ...])  Return the bitwise OR of the values provided in the
                           argument list.  There must be at least two.

       rshift(val, count)  Return the value of val, shifted right by count
                           bits.

       xor(v1, v2 [, ...]) Return the bitwise XOR of the values provided in
                           the argument list.  There must be at least two.

   Type Functions
       The following function is for use with multidimensional arrays.

       isarray(x)
              Return true if x is an array, false otherwise.

       You can tell the type of any variable or array element with the
       following function:

       typeof(x)
              Return a string indicating the type of x.  The string will be
              one of "array", "number", "regexp", "string", "strnum", or
              "undefined".

   Internationalization Functions
       The following functions may be used from within your AWK program for
       translating strings at run-time.  For full details, see GAWK: Effective
       AWK Programming.

       bindtextdomain(directory [, domain])
              Specify the directory where gawk looks for the .gmo files, in
              case they will not or cannot be placed in the ``standard''
              locations (e.g., during testing).  It returns the directory
              where domain is ``bound.''
              The default domain is the value of TEXTDOMAIN.  If directory is
              the null string (""), then bindtextdomain() returns the current
              binding for the given domain.

       dcgettext(string [, domain [, category]])
              Return the translation of string in text domain domain for
              locale category category.  The default value for domain is the
              current value of TEXTDOMAIN.  The default value for category is
              "LC_MESSAGES".
              If you supply a value for category, it must be a string equal to
              one of the known locale categories described in GAWK: Effective
              AWK Programming.  You must also supply a text domain.  Use
              TEXTDOMAIN if you want to use the current domain.

       dcngettext(string1, string2, number [, domain [, category]])
              Return the plural form used for number of the translation of
              string1 and string2 in text domain domain for locale category
              category.  The default value for domain is the current value of
              TEXTDOMAIN.  The default value for category is "LC_MESSAGES".
              If you supply a value for category, it must be a string equal to
              one of the known locale categories described in GAWK: Effective
              AWK Programming.  You must also supply a text domain.  Use
              TEXTDOMAIN if you want to use the current domain.

USER-DEFINED FUNCTIONS
       Functions in AWK are defined as follows:

              function name(parameter list) { statements }

       Functions execute when they are called from within expressions in
       either patterns or actions.  Actual parameters supplied in the function
       call are used to instantiate the formal parameters declared in the
       function.  Arrays are passed by reference, other variables are passed
       by value.

       Since functions were not originally part of the AWK language, the
       provision for local variables is rather clumsy: They are declared as
       extra parameters in the parameter list.  The convention is to separate
       local variables from real parameters by extra spaces in the parameter
       list.  For example:

              function  f(p, q,     a, b)   # a and b are local
              {
                   ...
              }

              /abc/     { ... ; f(1, 2) ; ... }

       The left parenthesis in a function call is required to immediately
       follow the function name, without any intervening whitespace.  This
       avoids a syntactic ambiguity with the concatenation operator.  This
       restriction does not apply to the built-in functions listed above.

       Functions may call each other and may be recursive.  Function
       parameters used as local variables are initialized to the null string
       and the number zero upon function invocation.

       Use return expr to return a value from a function.  The return value is
       undefined if no value is provided, or if the function returns by
       “falling off” the end.

       As a gawk extension, functions may be called indirectly. To do this,
       assign the name of the function to be called, as a string, to a
       variable.  Then use the variable as if it were the name of a function,
       prefixed with an @ sign, like so:
              function myfunc()
              {
                   print "myfunc called"
                   ...
              }

              {    ...
                   the_func = "myfunc"
                   @the_func()    # call through the_func to myfunc
                   ...
              }
       As of version 4.1.2, this works with user-defined functions, built-in
       functions, and extension functions.

       If --lint has been provided, gawk warns about calls to undefined
       functions at parse time, instead of at run time.  Calling an undefined
       function at run time is a fatal error.

       The word func may be used in place of function, although this is
       deprecated.

DYNAMICALLY LOADING NEW FUNCTIONS
       You can dynamically add new built-in functions to the running gawk
       interpreter with the @load statement.  The full details are beyond the
       scope of this manual page; see GAWK: Effective AWK Programming.

SIGNALS
       The gawk profiler accepts two signals.  SIGUSR1 causes it to dump a
       profile and function call stack to the profile file, which is either
       awkprof.out, or whatever file was named with the --profile option.  It
       then continues to run.  SIGHUP causes gawk to dump the profile and
       function call stack and then exit.

INTERNATIONALIZATION
       String constants are sequences of characters enclosed in double quotes.
       In non-English speaking environments, it is possible to mark strings in
       the AWK program as requiring translation to the local natural language.
       Such strings are marked in the AWK program with a leading underscore
       (“_”).  For example,

              gawk 'BEGIN { print "hello, world" }'

       always prints hello, world.  But,

              gawk 'BEGIN { print _"hello, world" }'

       might print bonjour, monde in France.

       There are several steps involved in producing and running a localizable
       AWK program.

       1.  Add a BEGIN action to assign a value to the TEXTDOMAIN variable to
           set the text domain to a name associated with your program:

                BEGIN { TEXTDOMAIN = "myprog" }

           This allows gawk to find the .gmo file associated with your
           program.  Without this step, gawk uses the messages text domain,
           which likely does not contain translations for your program.

       2.  Mark all strings that should be translated with leading
           underscores.

       3.  If necessary, use the dcgettext() and/or bindtextdomain() functions
           in your program, as appropriate.

       4.  Run gawk --gen-pot -f myprog.awk > myprog.pot to generate a .pot
           file for your program.

       5.  Provide appropriate translations, and build and install the
           corresponding .gmo files.

       The internationalization features are described in full detail in GAWK:
       Effective AWK Programming.

POSIX COMPATIBILITY
       A primary goal for gawk is compatibility with the POSIX standard, as
       well as with the latest version of Brian Kernighan's awk.  To this end,
       gawk incorporates the following user visible features which are not
       described in the AWK book, but are part of the Brian Kernighan's
       version of awk, and are in the POSIX standard.

       The book indicates that command line variable assignment happens when
       awk would otherwise open the argument as a file, which is after the
       BEGIN rule is executed.  However, in earlier implementations, when such
       an assignment appeared before any file names, the assignment would
       happen before the BEGIN rule was run.  Applications came to depend on
       this “feature.”  When awk was changed to match its documentation, the
       -v option for assigning variables before program execution was added to
       accommodate applications that depended upon the old behavior.  (This
       feature was agreed upon by both the Bell Laboratories and the GNU
       developers.)

       When processing arguments, gawk uses the special option “--” to signal
       the end of arguments.  In compatibility mode, it warns about but
       otherwise ignores undefined options.  In normal operation, such
       arguments are passed on to the AWK program for it to process.

       The AWK book does not define the return value of srand().  The POSIX
       standard has it return the seed it was using, to allow keeping track of
       random number sequences.  Therefore srand() in gawk also returns its
       current seed.

       Other features are: The use of multiple -f options (from MKS awk); the
       ENVIRON array; the \a, and \v escape sequences (done originally in gawk
       and fed back into the Bell Laboratories version); the tolower() and
       toupper() built-in functions (from the Bell Laboratories version); and
       the ISO C conversion specifications in printf (done first in the Bell
       Laboratories version).

HISTORICAL FEATURES
       There is one feature of historical AWK implementations that gawk
       supports: It is possible to call the length() built-in function not
       only with no argument, but even without parentheses!  Thus,

              a = length     # Holy Algol 60, Batman!

       is the same as either of

              a = length()
              a = length($0)

       Using this feature is poor practice, and gawk issues a warning about
       its use if --lint is specified on the command line.

GNU EXTENSIONS
       Gawk has a too-large number of extensions to POSIX awk.  They are
       described in this section.  All the extensions described here can be
       disabled by invoking gawk with the --traditional or --posix options.

       The following features of gawk are not available in POSIX awk.

       · No path search is performed for files named via the -f option.
         Therefore the AWKPATH environment variable is not special.

       · There is no facility for doing file inclusion (gawk's @include
         mechanism).

       · There is no facility for dynamically adding new functions written in
         C (gawk's @load mechanism).

       · The \x escape sequence.

       · The ability to continue lines after ?  and :.

       · Octal and hexadecimal constants in AWK programs.

       · The ARGIND, BINMODE, ERRNO, LINT, PREC, ROUNDMODE, RT and TEXTDOMAIN
         variables are not special.

       · The IGNORECASE variable and its side-effects are not available.

       · The FIELDWIDTHS variable and fixed-width field splitting.

       · The FPAT variable and field splitting based on field values.

       · The FUNCTAB, SYMTAB, and PROCINFO arrays are not available.

       · The use of RS as a regular expression.

       · The special file names available for I/O redirection are not
         recognized.

       · The |& operator for creating coprocesses.

       · The BEGINFILE and ENDFILE special patterns are not available.

       · The ability to split out individual characters using the null string
         as the value of FS, and as the third argument to split().

       · An optional fourth argument to split() to receive the separator
         texts.

       · The optional second argument to the close() function.

       · The optional third argument to the match() function.

       · The ability to use positional specifiers with printf and sprintf().

       · The ability to pass an array to length().

       · The and(), asort(), asorti(), bindtextdomain(), compl(), dcgettext(),
         dcngettext(), gensub(), lshift(), mktime(), or(), patsplit(),
         rshift(), strftime(), strtonum(), systime() and xor() functions.

       · Localizable strings.

       · Non-fatal I/O.

       · Retryable I/O.

       The AWK book does not define the return value of the close() function.
       Gawk's close() returns the value from fclose(3), or pclose(3), when
       closing an output file or pipe, respectively.  It returns the process's
       exit status when closing an input pipe.  The return value is -1 if the
       named file, pipe or coprocess was not opened with a redirection.

       When gawk is invoked with the --traditional option, if the fs argument
       to the -F option is “t”, then FS is set to the tab character.  Note
       that typing gawk -F\t ...  simply causes the shell to quote the “t,”
       and does not pass “\t” to the -F option.  Since this is a rather ugly
       special case, it is not the default behavior.  This behavior also does
       not occur if --posix has been specified.  To really get a tab character
       as the field separator, it is best to use single quotes: gawk -F'\t'
       ....

ENVIRONMENT VARIABLES
       The AWKPATH environment variable can be used to provide a list of
       directories that gawk searches when looking for files named via the -f,
       --file, -i and --include options, and the @include directive.  If the
       initial search fails, the path is searched again after appending .awk
       to the filename.

       The AWKLIBPATH environment variable can be used to provide a list of
       directories that gawk searches when looking for files named via the -l
       and --load options.

       The GAWK_READ_TIMEOUT environment variable can be used to specify a
       timeout in milliseconds for reading input from a terminal, pipe or two-
       way communication including sockets.

       For connection to a remote host via socket, GAWK_SOCK_RETRIES controls
       the number of retries, and GAWK_MSEC_SLEEP and the interval between
       retries.  The interval is in milliseconds. On systems that do not
       support usleep(3), the value is rounded up to an integral number of
       seconds.

       If POSIXLY_CORRECT exists in the environment, then gawk behaves exactly
       as if --posix had been specified on the command line.  If --lint has
       been specified, gawk issues a warning message to this effect.

EXIT STATUS
       If the exit statement is used with a value, then gawk exits with the
       numeric value given to it.

       Otherwise, if there were no problems during execution, gawk exits with
       the value of the C constant EXIT_SUCCESS.  This is usually zero.

       If an error occurs, gawk exits with the value of the C constant
       EXIT_FAILURE.  This is usually one.

       If gawk exits because of a fatal error, the exit status is 2.  On non-
       POSIX systems, this value may be mapped to EXIT_FAILURE.

VERSION INFORMATION
       This man page documents gawk, version 4.2.

AUTHORS
       The original version of UNIX awk was designed and implemented by Alfred
       Aho, Peter Weinberger, and Brian Kernighan of Bell Laboratories.  Brian
       Kernighan continues to maintain and enhance it.

       Paul Rubin and Jay Fenlason, of the Free Software Foundation, wrote
       gawk, to be compatible with the original version of awk distributed in
       Seventh Edition UNIX.  John Woods contributed a number of bug fixes.
       David Trueman, with contributions from Arnold Robbins, made gawk
       compatible with the new version of UNIX awk.  Arnold Robbins is the
       current maintainer.

       See GAWK: Effective AWK Programming for a full list of the contributors
       to gawk and its documentation.

       See the README file in the gawk distribution for up-to-date information
       about maintainers and which ports are currently supported.

BUG REPORTS
       If you find a bug in gawk, please send electronic mail to bug-
       gawk@gnu.org.  Please include your operating system and its revision,
       the version of gawk (from gawk --version), which C compiler you used to
       compile it, and a test program and data that are as small as possible
       for reproducing the problem.

       Before sending a bug report, please do the following things.  First,
       verify that you have the latest version of gawk.  Many bugs (usually
       subtle ones) are fixed at each release, and if yours is out of date,
       the problem may already have been solved.  Second, please see if
       setting the environment variable LC_ALL to LC_ALL=C causes things to
       behave as you expect. If so, it's a locale issue, and may or may not
       really be a bug.  Finally, please read this man page and the reference
       manual carefully to be sure that what you think is a bug really is,
       instead of just a quirk in the language.

       Whatever you do, do NOT post a bug report in comp.lang.awk.  While the
       gawk developers occasionally read this newsgroup, posting bug reports
       there is an unreliable way to report bugs.  Instead, please use the
       electronic mail addresses given above.  Really.

       If you're using a GNU/Linux or BSD-based system, you may wish to submit
       a bug report to the vendor of your distribution.  That's fine, but
       please send a copy to the official email address as well, since there's
       no guarantee that the bug report will be forwarded to the gawk
       maintainer.

BUGS
       The -F option is not necessary given the command line variable
       assignment feature; it remains only for backwards compatibility.

SEE ALSO
       egrep(1), sed(1), getpid(2), getppid(2), getpgrp(2), getuid(2),
       geteuid(2), getgid(2), getegid(2), getgroups(2), printf(3),
       strftime(3), usleep(3)

       The AWK Programming Language, Alfred V. Aho, Brian W. Kernighan, Peter
       J. Weinberger, Addison-Wesley, 1988.  ISBN 0-201-07981-X.

       GAWK: Effective AWK Programming, Edition 4.2, shipped with the gawk
       source.  The current version of this document is available online at
       https://www.gnu.org/software/gawk/manual.

       The GNU gettext documentation, available online at
       https://www.gnu.org/software/gettext.

EXAMPLES
       Print and sort the login names of all users:

            BEGIN     { FS = ":" }
                 { print $1 | "sort" }

       Count lines in a file:

                 { nlines++ }
            END  { print nlines }

       Precede each line by its number in the file:

            { print FNR, $0 }

       Concatenate and line number (a variation on a theme):

            { print NR, $0 }

       Run an external command for particular lines of data:

            tail -f access_log |
            awk '/myhome.html/ { system("nmap " $1 ">> logdir/myhome.html") }'

ACKNOWLEDGEMENTS
       Brian Kernighan provided valuable assistance during testing and
       debugging.  We thank him.

COPYING PERMISSIONS
       Copyright © 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
       2001, 2002, 2003, 2004, 2005, 2007, 2009, 2010, 2011, 2012, 2013, 2014,
       2015, 2016, 2017, 2018 Free Software Foundation, Inc.

       Permission is granted to make and distribute verbatim copies of this
       manual page provided the copyright notice and this permission notice
       are preserved on all copies.

       Permission is granted to copy and distribute modified versions of this
       manual page under the conditions for verbatim copying, provided that
       the entire resulting derived work is distributed under the terms of a
       permission notice identical to this one.

       Permission is granted to copy and distribute translations of this
       manual page into another language, under the above conditions for
       modified versions, except that this permission notice may be stated in
       a translation approved by the Foundation.



Free Software Foundation          Feb 15 2018                          GAWK(1)