library(n) Tcl (8.0) library(n)
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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 |
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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 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 by the
name cmd. This command examines the directories in the
current search path (given by the PATH environment
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library(n) Tcl (8.0) library(n)
variable) to see if there is an executable file named
cmd in any of those directories. If so, it returns 1;
if not it returns 0. 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 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. 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 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
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library(n) Tcl (8.0) library(n)
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
init.tcl to see how this works.
Auto_mkindex_old 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 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.
varName
tcl_findLibrary basename version patch initScript enVarName
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
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library(n) Tcl (8.0) library(n)
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:
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
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library(n) Tcl (8.0) library(n)
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 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 giving
directories to search during auto-load operations.
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_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.
unknown_active
This variable is set by unknown to indicate that it is
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library(n) Tcl (8.0) library(n)
active. It is used to detect errors where unknown
recurses on itself infinitely. The variable is unset
before unknown returns.
KEYWORDS
auto-exec, auto-load, library, unknown, word, whitespace
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