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
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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 proce-
dures 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 com-
mand
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 im-
ported commands specified by pattern reside in an autoloaded li-
brary. 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 eval-
uate 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 suc-
cessfully 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
child 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 defini-
tions that do not appear in this way (e.g. they have spaces be-
fore the proc) will not be indexed. If your script contains
“dangerous” code, such as global initialization code or proce-
dure 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 name-
space, and then in the global namespace. Accordingly, if com-
mand is relative and namespace is not ::, the list returned has
two elements: command scoped by namespace, as if it were a com-
mand 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 base-
nameversion (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 environ-
ment 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 paral-
lel build tree.
parray arrayName ?pattern?
Prints on standard output the names and values of all the ele-
ments in the array arrayName, or just the names that match pat-
tern (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_nonword-
chars below for more details on how Tcl determines which charac-
ters are word characters.
tcl_startOfNextWord str start
Returns the index of the first start-of-word location that oc-
curs after a starting index start in the string str. A start-
of-word location is defined to be the first word character fol-
lowing 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 oc-
curs 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 particu-
lar 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 in-
dex 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_pkg-
Path variable. Additional locations to look for files and pack-
age indices should normally be added to this variable using lap-
pend.
env(TCL_LIBRARY)
If set, then it specifies the location of the directory contain-
ing library scripts (the value of this variable will be assigned
to the tcl_library variable and therefore returned by the com-
mand 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, re-
gardless of platform. This variable is only used when initial-
izing 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 rou-
tines like tcl_endOfWord to identify whether a character is part
of a word or not. If the pattern matches a character, the char-
acter 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 un-
derscores are considered non-word characters.
tcl_wordchars
This variable contains a regular expression that is used by rou-
tines like tcl_endOfWord to identify whether a character is part
of a word or not. If the pattern matches a character, the char-
acter is considered to be a word character. On Windows plat-
forms, 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)
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