library(n) Tcl Built-In Commands library(n)
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NAME
auto_execok, auto_import, auto_load, auto_mkindex, auto_mkindex_old, auto_qualify, auto_reset,
tcl_findLibrary, parray, tcl_endOfWord, tcl_startOfNextWord, tcl_startOfPreviousWord, tcl_word-BreakAfter, tcl_wordBreakAfter,
BreakAfter, tcl_wordBreakBefore - standard library of Tcl procedures
SYNOPSIS
auto_execok cmd
auto_import pattern
auto_load cmd
auto_mkindex dir pattern pattern ...
auto_mkindex_old dir pattern pattern ...
auto_qualify command namespace
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 |
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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 appli-cation application
cation 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 hap-pens happens
pens 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 directo-ries directories
ries 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 direc-tories directories
tories and file extensions as used by exec. Auto_exec 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 infor-mation. information.
mation.
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 cre-ated. created.
ated. The command returns 0 if there was no index entry for cmd or if the script didn't actu-ally actually
ally 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 informa-tion information
tion 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), gen-erates generates
erates 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 parses the Tcl scripts in a relatively unsophisticated way: if any line con-tains contains
tains 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. 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're
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 names-pace namespace
pace 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 run-time. runtime.
time.
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
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 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 fol- |
lowing 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 char- |
acters. |
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 follow- |
ing 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 bound- |
ary.
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 exe-cutable executable
cutable 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. 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 vari-able, variable,
able, the parent directory of $tcl_library, the directories listed in the $tcl_pkgPath vari-able. variable.
able.
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 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.
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_word- |
chars | |
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.
unknown_pending
Used by unknown to record the command(s) for which it is searching. It is used to detect
errors where unknown recurses on itself infinitely. The variable is unset before unknown
returns.
SEE ALSO
info(n), re_syntax(n)
KEYWORDS
auto-exec, auto-load, library, unknown, word, whitespace
Tcl 8.0 library(n)
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