NAME
       library - standard library of Tcl procedures

SYNOPSIS
       auto_execok cmd
       auto_load cmd
       auto_mkindex dir pattern pattern ...
       auto_mkindex_old dir pattern pattern ...
       auto_reset
       tcl_findLibrary basename version patch initScript enVarName varName
       parray arrayName
       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 differ-
       ent 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 applica-
       tion 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 automat-
       ically.  The code in init.tcl will define the unknown pro-
       cedure 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_exec remembers information about previ-
              ous 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_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.  Other-
              wise 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 gener-
              ated 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 didn't 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  com-
              mands  that  can contribute to the auto_load index.
              You will have to read through init.tcl to  see  how
              this works.

              Auto_mkindex_old  parses the Tcl scripts in a rela-
              tively 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 don't appear in this way
              (e.g. they have spaces before the proc) will not be
              indexed.

       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're used.

       tcl_findLibrary  basename version patch initScript
              enVarName var- Name
              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  inter-
              preter  once  it  is found.  The directory in which
              this file is found is stored into the global  vari-
              able  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
              Prints on standard output the names and  values  of
              all the elements in the array arrayName.  ArrayName
              must be an array accessible to the caller  of  par-
              ray.  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  loca-
              tion  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  loca-
              tion  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:

       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  giv-
              ing  directories  to search during auto-load opera-
              tions.  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  variable,  the parent
              directory of $tcl_library, the  directories  listed
              in the $tcl_pkgPath variable.

       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  isn't  set  then  a
              default value is used.

       env(TCLLIBPATH)
              If set, then it must contain a valid Tcl list  giv-
              ing  directories  to search during auto-load opera-
              tions.  This variable is only used when  initializ-
              ing the auto_path variable.

       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  consid-
              ered  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  under-
              scores.

       unknown_active
              This variable is set by unknown to indicate that it
              is active.  It  is  used  to  detect  errors  where
              unknown  recurses  on itself infinitely.  The vari-
              able is unset before unknown returns.


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