library

library(3tcl)                Tcl Built-In Commands               library(3tcl)



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NAME
       auto_execok, auto_import, auto_load, auto_mkindex, auto_qualify,
       auto_reset, tcl_findLibrary, parray, tcl_endOfWord,
       tcl_startOfNextWord, tcl_startOfPreviousWord, tcl_wordBreakAfter,
       tcl_wordBreakBefore - standard library of Tcl procedures

SYNOPSIS
       auto_execok cmd
       auto_import pattern
       auto_load cmd
       auto_mkindex dir pattern pattern ...
       auto_qualify command namespace
       auto_reset
       tcl_findLibrary basename version patch initScript enVarName varName
       parray arrayName ?pattern?
       tcl_endOfWord str start
       tcl_startOfNextWord str start
       tcl_startOfPreviousWord str start
       tcl_wordBreakAfter str start
       tcl_wordBreakBefore str start
______________________________________________________________________________

INTRODUCTION
       Tcl includes a library of Tcl procedures for commonly-needed functions.
       The procedures defined in the Tcl library are generic ones suitable for
       use by many different applications.  The location of the Tcl library is
       returned by the info library command.  In addition to the Tcl library,
       each application will normally have its own library of support
       procedures as well;  the location of this library is normally given by
       the value of the $app_library global variable, where app is the name of
       the application.  For example, the location of the Tk library is kept
       in the variable tk_library.

       To access the procedures in the Tcl library, an application should
       source the file init.tcl in the library, for example with the Tcl
       command

              source [file join [info library] init.tcl]

       If the library procedure Tcl_Init is invoked from an application's
       Tcl_AppInit procedure, this happens automatically.  The code in
       init.tcl will define the unknown procedure and arrange for the other
       procedures to be loaded on-demand using the auto-load mechanism defined
       below.

COMMAND PROCEDURES
       The following procedures are provided in the Tcl library:

       auto_execok cmd
              Determines whether there is an executable file or shell builtin
              by the name cmd.  If so, it returns a list of arguments to be
              passed to exec to execute the executable file or shell builtin
              named by cmd.  If not, it returns an empty string.  This command
              examines the directories in the current search path (given by
              the PATH environment variable) in its search for an executable
              file named cmd.  On Windows platforms, the search is expanded
              with the same directories and file extensions as used by exec.
              Auto_execok remembers information about previous searches in an
              array named auto_execs;  this avoids the path search in future
              calls for the same cmd.  The command auto_reset may be used to
              force auto_execok to forget its cached information.

       auto_import pattern
              Auto_import is invoked during namespace import to see if the
              imported commands specified by pattern reside in an autoloaded
              library.  If so, the commands are loaded so that they will be
              available to the interpreter for creating the import links.  If
              the commands do not reside in an autoloaded library, auto_import
              does nothing.  The pattern matching is performed according to
              the matching rules of namespace import.

       auto_load cmd
              This command attempts to load the definition for a Tcl command
              named cmd.  To do this, it searches an auto-load path, which is
              a list of one or more directories.  The auto-load path is given
              by the global variable auto_path if it exists.  If there is no
              auto_path variable, then the TCLLIBPATH environment variable is
              used, if it exists.  Otherwise the auto-load path consists of
              just the Tcl library directory.  Within each directory in the
              auto-load path there must be a file tclIndex that describes one
              or more commands defined in that directory and a script to
              evaluate to load each of the commands.  The tclIndex file should
              be generated with the auto_mkindex command.  If cmd is found in
              an index file, then the appropriate script is evaluated to
              create the command.  The auto_load command returns 1 if cmd was
              successfully created.  The command returns 0 if there was no
              index entry for cmd or if the script did not actually define cmd
              (e.g. because index information is out of date).  If an error
              occurs while processing the script, then that error is returned.
              Auto_load only reads the index information once and saves it in
              the array auto_index;  future calls to auto_load check for cmd
              in the array rather than re-reading the index files.  The cached
              index information may be deleted with the command auto_reset.
              This will force the next auto_load command to reload the index
              database from disk.

       auto_mkindex dir pattern pattern ...
              Generates an index suitable for use by auto_load.  The command
              searches dir for all files whose names match any of the pattern
              arguments (matching is done with the glob command), generates an
              index of all the Tcl command procedures defined in all the
              matching files, and stores the index information in a file named
              tclIndex in dir. If no pattern is given a pattern of *.tcl will
              be assumed.  For example, the command

                     auto_mkindex foo *.tcl

              will read all the .tcl files in subdirectory foo and generate a
              new index file foo/tclIndex.

              Auto_mkindex parses the Tcl scripts by sourcing them into a
              slave interpreter and monitoring the proc and namespace commands
              that are executed.  Extensions can use the (undocumented)
              auto_mkindex_parser package to register other commands that can
              contribute to the auto_load index. You will have to read through
              auto.tcl to see how this works.

              Auto_mkindex_old (which has the same syntax as auto_mkindex)
              parses the Tcl scripts in a relatively unsophisticated way:  if
              any line contains the word “proc” as its first characters then
              it is assumed to be a procedure definition and the next word of
              the line is taken as the procedure's name.  Procedure
              definitions that do not appear in this way (e.g. they have
              spaces before the proc) will not be indexed.  If your script
              contains “dangerous” code, such as global initialization code or
              procedure names with special characters like $, *, [ or ], you
              are safer using auto_mkindex_old.

       auto_reset
              Destroys all the information cached by auto_execok and
              auto_load.  This information will be re-read from disk the next
              time it is needed.  Auto_reset also deletes any procedures
              listed in the auto-load index, so that fresh copies of them will
              be loaded the next time that they are used.

       auto_qualify command namespace
              Computes a list of fully qualified names for command.  This list
              mirrors the path a standard Tcl interpreter follows for command
              lookups:  first it looks for the command in the current
              namespace, and then in the global namespace.  Accordingly, if
              command is relative and namespace is not ::, the list returned
              has two elements:  command scoped by namespace, as if it were a
              command in the namespace namespace; and command as if it were a
              command in the global namespace.  Otherwise, if either command
              is absolute (it begins with ::), or namespace is ::, the list
              contains only command as if it were a command in the global
              namespace.

              Auto_qualify is used by the auto-loading facilities in Tcl, both
              for producing auto-loading indexes such as pkgIndex.tcl, and for
              performing the actual auto-loading of functions at runtime.

       tcl_findLibrary basename version patch initScript enVarName varName
              This is a standard search procedure for use by extensions during
              their initialization.  They call this procedure to look for
              their script library in several standard directories.  The last
              component of the name of the library directory is normally
              basenameversion (e.g., tk8.0), but it might be “library” when in
              the build hierarchies.  The initScript file will be sourced into
              the interpreter once it is found.  The directory in which this
              file is found is stored into the global variable varName.  If
              this variable is already defined (e.g., by C code during
              application initialization) then no searching is done.
              Otherwise the search looks in these directories: the directory
              named by the environment variable enVarName; relative to the Tcl
              library directory; relative to the executable file in the
              standard installation bin or bin/arch directory; relative to the
              executable file in the current build tree; relative to the
              executable file in a parallel build tree.

       parray arrayName ?pattern?
              Prints on standard output the names and values of all the
              elements in the array arrayName, or just the names that match
              pattern (using the matching rules of string match) and their
              values if pattern is given.  ArrayName must be an array
              accessible to the caller of parray.  It may be either local or
              global.

       tcl_endOfWord str start
              Returns the index of the first end-of-word location that occurs
              after a starting index start in the string str.  An end-of-word
              location is defined to be the first non-word character following
              the first word character after the starting point.  Returns -1
              if there are no more end-of-word locations after the starting
              point.  See the description of tcl_wordchars and
              tcl_nonwordchars below for more details on how Tcl determines
              which characters are word characters.

       tcl_startOfNextWord str start
              Returns the index of the first start-of-word location that
              occurs after a starting index start in the string str.  A start-
              of-word location is defined to be the first word character
              following a non-word character.  Returns -1 if there are no more
              start-of-word locations after the starting point.

       tcl_startOfPreviousWord str start
              Returns the index of the first start-of-word location that
              occurs before a starting index start in the string str.  Returns
              -1 if there are no more start-of-word locations before the
              starting point.

       tcl_wordBreakAfter str start
              Returns the index of the first word boundary after the starting
              index start in the string str.  Returns -1 if there are no more
              boundaries after the starting point in the given string.  The
              index returned refers to the second character of the pair that
              comprises a boundary.

       tcl_wordBreakBefore str start
              Returns the index of the first word boundary before the starting
              index start in the string str.  Returns -1 if there are no more
              boundaries before the starting point in the given string.  The
              index returned refers to the second character of the pair that
              comprises a boundary.

VARIABLES
       The following global variables are defined or used by the procedures in
       the Tcl library. They fall into two broad classes, handling unknown
       commands and packages, and determining what are words.

   AUTOLOADING AND PACKAGE MANAGEMENT VARIABLES
       auto_execs
              Used by auto_execok to record information about whether
              particular commands exist as executable files.

       auto_index
              Used by auto_load to save the index information read from disk.

       auto_noexec
              If set to any value, then unknown will not attempt to auto-exec
              any commands.

       auto_noload
              If set to any value, then unknown will not attempt to auto-load
              any commands.

       auto_path
              If set, then it must contain a valid Tcl list giving directories
              to search during auto-load operations (including for package
              index files when using the default package unknown handler).
              This variable is initialized during startup to contain, in
              order: the directories listed in the TCLLIBPATH environment
              variable, the directory named by the tcl_library global
              variable, the parent directory of tcl_library, the directories
              listed in the tcl_pkgPath variable.  Additional locations to
              look for files and package indices should normally be added to
              this variable using lappend.

       env(TCL_LIBRARY)
              If set, then it specifies the location of the directory
              containing library scripts (the value of this variable will be
              assigned to the tcl_library variable and therefore returned by
              the command info library).  If this variable is not set then a
              default value is used.

       env(TCLLIBPATH)
              If set, then it must contain a valid Tcl list giving directories
              to search during auto-load operations.  Directories must be
              specified in Tcl format, using “/” as the path separator,
              regardless of platform.  This variable is only used when
              initializing the auto_path variable.

   WORD BOUNDARY DETERMINATION VARIABLES
       These variables are only used in the tcl_endOfWord,
       tcl_startOfNextWord, tcl_startOfPreviousWord, tcl_wordBreakAfter, and
       tcl_wordBreakBefore commands.

       tcl_nonwordchars
              This variable contains a regular expression that is used by
              routines like tcl_endOfWord to identify whether a character is
              part of a word or not.  If the pattern matches a character, the
              character is considered to be a non-word character.  On Windows
              platforms, spaces, tabs, and newlines are considered non-word
              characters.  Under Unix, everything but numbers, letters and
              underscores are considered non-word characters.

       tcl_wordchars
              This variable contains a regular expression that is used by
              routines like tcl_endOfWord to identify whether a character is
              part of a word or not.  If the pattern matches a character, the
              character is considered to be a word character.  On Windows
              platforms, words are comprised of any character that is not a
              space, tab, or newline.  Under Unix, words are comprised of
              numbers, letters or underscores.

SEE ALSO
       env(3tcl), info(3tcl), re_syntax(3tcl)

KEYWORDS
       auto-exec, auto-load, library, unknown, word, whitespace



Tcl                                   8.0                        library(3tcl)