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_reset
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 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 by
the name cmd. This command examines the directo-
ries in the current search path (given by the PATH
environment variable) to see if there is an exe-
cutable 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. 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 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.
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.
env(TCL_LIBRARY)
If set, then it specifies the location of the
directory containing library scripts (the value of
this variable will be 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 if auto_path is
not defined.
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