'\"
'\" Copyright (c) 1991-1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH library n "8.0" Tcl "Tcl Built-In Commands"
.so man.macros
.BS
.SH NAME
auto_execok, auto_import, auto_load, auto_mkindex, auto_qualify, auto_reset, foreachLine, parray, readFile, tcl_findLibrary, tcl_endOfWord, tcl_nonwordchars, tcl_startOfNextWord, tcl_startOfPreviousWord, tcl_wordBreakAfter, tcl_wordBreakBefore, tcl_wordchars, writeFile \- Standard library of Tcl procedures
.SH SYNOPSIS
.nf
\fBauto_execok \fIcmd\fR
\fBauto_import \fIpattern\fR
\fBauto_load \fIcmd\fR
\fBauto_mkindex \fIdir pattern pattern ...\fR
\fBauto_qualify \fIcommand namespace\fR
\fBauto_reset\fR
\fBtcl_findLibrary \fIbasename version patch initScript enVarName varName\fR
\fBparray \fIarrayName\fR ?\fIpattern\fR?
\fBtcl_endOfWord \fIstr start\fR
\fBtcl_startOfNextWord \fIstr start\fR
\fBtcl_startOfPreviousWord \fIstr start\fR
\fBtcl_wordBreakAfter \fIstr start\fR
\fBtcl_wordBreakBefore \fIstr start\fR
.VS TIP670
\fBforeachLine \fIfilename varName body\fR
\fBreadFile \fIfilename\fR ?\fBtext\fR|\fBbinary\fR?
\fBwriteFile \fIfilename\fR ?\fBtext\fR|\fBbinary\fR? \fIcontents\fR
.VE TIP670
.fi
.BE
.SH INTRODUCTION
.PP
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 \fBinfo library\fR
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 \fB$\fIapp\fB_library\fR
global variable, where \fIapp\fR is the name of the application.
For example, the location of the Tk library is kept in the variable
\fBtk_library\fR.
.PP
To access the procedures in the Tcl library, an application should
source the file \fBinit.tcl\fR in the library, for example with
the Tcl command
.PP
.CS
\fBsource [file join [info library] init.tcl]\fR
.CE
.PP
If the library procedure \fBTcl_Init\fR is invoked from an application's
\fBTcl_AppInit\fR procedure, this happens automatically.
The code in \fBinit.tcl\fR will define the \fBunknown\fR procedure
and arrange for the other procedures to be loaded on-demand using
the auto-load mechanism defined below.
.SH "COMMAND PROCEDURES"
.PP
The following procedures are provided in the Tcl library:
.\" COMMAND: auto_execok
.TP
\fBauto_execok \fIcmd\fR
.
The command returns a list of arguments to be passed to \fBexec\fR to
execute the external program named by \fIcmd\fR. If no such program is
found, the command returns an empty list. Callers must not make any
assumptions about any returned paths being in any particular form such
as normalized, absolute, native or canonical.
.RS
.PP
On platforms other than Windows, if \fIcmd\fR contains any path
separators, \fBauto_execok\fR checks for the existence of an executable
file with that path. If present, it is returned as the first element of
the returned list. Note that this may be a relative path. If \fIcmd\fR
does not contain any path separators, all directories in the \fBPATH\fR
environment variable are searched for an executable file of that name.
If found, a list containing a single element holding the full path to
the file is returned.
.PP
The rest of this description applies to Windows platforms.
.PP
If \fIcmd\fR contains path separators, the command checks for the
existence of a file of that name. If found, the file associations in the
Windows registry is looked up to retrieve the template for the file's
extension. On success, the template is processed to replace environment
variables, placeholders for the file path, converted to list form and
returned. Otherwise, an empty list is returned.
.PP
If \fIcmd\fR does not contain path separators, it is first matched
against the built-in commands in the \fBcmd.exe\fR command shell.
Built-ins that are intended only for batch file use are excluded. On a
match, the returned list is the list of arguments to be passed to
\fBexec\fR to run the built-in using \fBcmd.exe\fR.
.PP
Next, \fBauto_execok\fR searches directories in the following order:
the directory of the process executable, the current working directory
(subject to conditions described below), the Windows \fBsystem32\fR
directory, the Windows directory and the directories in the \fBPATH\fR
environment variable. Within each directory, the command will look for
a file matching the passed name, and if not found, for a file matching
the passed name appended with extensions listed in the \fBPATHEXT\fR
environment variable. The extension of the matched file is looked up in
the file associations in the registry and the corresponding template is
returned after processing as described earlier.
.PP
Inclusion of the current working directory in the list of examined
directories depends on Windows system settings retrieved with the
\fBNeedCurrentDirectoryForExePathW\fR Win32 API. Refer to its
documentation for details. Note that if the current directory, \fB.\fR,
is explicitly included in \fBPATH\fR, it is not affected by this
setting.
.PP
Finally, if all above fails, \fIcmd\fR is looked up in the \fBApp
Paths\fR key in the Windows registry after appending \fB.exe\fR if not
already present. If listed there as a registered application, its path
is returned as the first (and only) list element.
.PP
To run the \fIDIR\fR shell builtin on Windows, you would do:
.PP
.CS
exec {*}[\fBauto_execok\fR dir]
.CE
.PP
To open a \fB.txt\fR file on Windows with the associated program,
you would do:
.PP
.CS
exec {*}[\fBauto_execok\fR path/to/foo.txt]
.CE
.PP
Note in the above that since \fB.txt\fR is not generally included in
\fBPATHEXT\fR, the passed name is not searched for even if it does not
include any path separators.
.PP
To discover if there is a \fIfrobnicate\fR that can be run by \fBexec\fR,
you would do:
.PP
.CS
set mayFrob [expr {[llength [\fBauto_execok\fR frobnicate]] > 0}]
.CE
.RE
.\" COMMAND: auto_import
.TP
\fBauto_import \fIpattern\fR
.
\fBAuto_import\fR is invoked during \fBnamespace import\fR to see if
the imported commands specified by \fIpattern\fR 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, \fBauto_import\fR
does nothing.  The pattern matching is performed according to the
matching rules of \fBnamespace import\fR.
.RS
.PP
It is not normally necessary to call this command directly.
.RE
.\" COMMAND: auto_load
.TP
\fBauto_load \fIcmd\fR
.
This command attempts to load the definition for a Tcl command named
\fIcmd\fR.  To do this, it searches an \fIauto-load path\fR, which is
a list of one or more directories.  The auto-load path is given by the
global variable \fBauto_path\fR if it exists (see the tclvars manual page).
If there is no
\fBauto_path\fR variable, then the \fBTCLLIBPATH\fR 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 \fBtclIndex\fR that describes one or more
commands defined in that directory and a script to evaluate to load
each of the commands.  The \fBtclIndex\fR file should be generated
with the \fBauto_mkindex\fR command.  If \fIcmd\fR is found in an
index file, then the appropriate script is evaluated to create the
command.  The \fBauto_load\fR command returns 1 if \fIcmd\fR was
successfully created.  The command returns 0 if there was no index
entry for \fIcmd\fR or if the script did not actually define \fIcmd\fR
(e.g. because index information is out of date).  If an error occurs
while processing the script, then that error is returned.
\fBAuto_load\fR only reads the index information once and saves it in
the array \fBauto_index\fR;  future calls to \fBauto_load\fR check for
\fIcmd\fR in the array rather than re-reading the index files.  The
cached index information may be deleted with the command
\fBauto_reset\fR.  This will force the next \fBauto_load\fR command to
reload the index database from disk.
.RS
.PP
It is not normally necessary to call this command directly; the
default \fBunknown\fR handler will do so.
.RE
.\" COMMAND: auto_mkindex
.TP
\fBauto_mkindex \fIdir pattern pattern ...\fR
.
Generates an index suitable for use by \fBauto_load\fR.  The command
searches \fIdir\fR for all files whose names match any of the
\fIpattern\fR arguments (matching is done with the \fBglob\fR
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 \fBtclIndex\fR in \fIdir\fR. If no pattern is given a pattern of
\fB*.tcl\fR will be assumed.  For example, the command
.RS
.PP
.CS
\fBauto_mkindex foo *.tcl\fR
.CE
.PP
will read all the \fB.tcl\fR files in subdirectory \fBfoo\fR and
generate a new index file \fBfoo/tclIndex\fR.
.PP
\fBAuto_mkindex\fR 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.
.PP
\fBAuto_mkindex_old\fR
(which has the same syntax as \fBauto_mkindex\fR)
parses the Tcl scripts in a relatively
unsophisticated way:  if any line contains the word
.QW \fBproc\fR
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 do not appear in this way (e.g.\ they
have spaces before the \fBproc\fR) will not be indexed.  If your
script contains
.QW dangerous
code, such as global initialization
code or procedure names with special characters like \fB$\fR,
\fB*\fR, \fB[\fR or \fB]\fR, you are safer using \fBauto_mkindex_old\fR.
.RE
.\" COMMAND: auto_reset
.TP
\fBauto_reset\fR
.
Destroys all the information cached by \fBauto_execok\fR and
\fBauto_load\fR.  This information will be re-read from disk the next
time it is needed.  \fBAuto_reset\fR 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.
.\" COMMAND: auto_qualify
.TP
\fBauto_qualify \fIcommand namespace\fR
.
Computes a list of fully qualified names for \fIcommand\fR.  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 \fIcommand\fR is
relative and \fInamespace\fR is not \fB::\fR, the list returned has
two elements:  \fIcommand\fR scoped by \fInamespace\fR, as if it were
a command in the \fInamespace\fR namespace; and \fIcommand\fR as if it
were a command in the global namespace.  Otherwise, if either
\fIcommand\fR is absolute (it begins with \fB::\fR), or
\fInamespace\fR is \fB::\fR, the list contains only \fIcommand\fR as
if it were a command in the global namespace.
.RS
.PP
\fBAuto_qualify\fR is used by the auto-loading facilities in Tcl, both
for producing auto-loading indexes such as \fIpkgIndex.tcl\fR, and for
performing the actual auto-loading of functions at runtime.
.RE
.\" COMMAND: auto_findLibrary
.TP
\fBtcl_findLibrary \fIbasename version patch initScript enVarName varName\fR
.
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 \fIbasenameversion\fR
(e.g., tk8.0), but it might be
.QW library
when in the build hierarchies.
The \fIpatch\fR argument is not used.
The \fIinitScript\fR 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 \fIvarName\fR.
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 \fIenVarName\fR;
relative to the Tcl library directory;
relative to the executable file in the standard installation
bin or bin/\fIarch\fR directory;
relative to the executable file in the current build tree;
relative to the executable file in a parallel build tree.
.\" COMMAND: parray
.TP
\fBparray \fIarrayName\fR ?\fIpattern\fR?
.
Prints on standard output the names and values of all the elements in the
array \fIarrayName\fR, or just the names that match \fIpattern\fR (using the
matching rules of \fBstring match\fR) and their values if \fIpattern\fR is
given.
\fIArrayName\fR must be an array accessible to the caller of \fBparray\fR.
It may be either local or global.
The result of this command is the empty string.
.RS
.PP
For example, to print the contents of the \fBtcl_platform\fR array, do:
.PP
.CS
\fBparray\fR tcl_platform
.CE
.RE
.SS "WORD BOUNDARY HELPERS"
.PP
These procedures are mainly used internally by Tk.
.\" COMMAND: tcl_endOfWord
.TP
\fBtcl_endOfWord \fIstr start\fR
.
Returns the index of the first end-of-word location that occurs after
a starting index \fIstart\fR in the string \fIstr\fR.  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 \fBtcl_wordchars\fR and \fBtcl_nonwordchars\fR below
for more details on how Tcl determines which characters are word
characters.
.\" COMMAND: tcl_startOfNextWord
.TP
\fBtcl_startOfNextWord \fIstr start\fR
.
Returns the index of the first start-of-word location that occurs
after a starting index \fIstart\fR in the string \fIstr\fR.  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.
.RS
.PP
For example, to print the indices of the starts of each word in a
string according to platform rules:
.PP
.CS
set theString "The quick brown fox"
for {set idx 0} {$idx >= 0} {
        set idx [\fBtcl_startOfNextWord\fR $theString $idx]} {
    puts "Word start index: $idx"
}
.CE
.RE
.\" COMMAND: tcl_startOfPreviousWord
.TP
\fBtcl_startOfPreviousWord \fIstr start\fR
.
Returns the index of the first start-of-word location that occurs
before a starting index \fIstart\fR in the string \fIstr\fR.  Returns
\-1 if there are no more start-of-word locations before the starting
point.
.\" COMMAND: tcl_wordBreakAfter
.TP
\fBtcl_wordBreakAfter \fIstr start\fR
.
Returns the index of the first word boundary after the starting index
\fIstart\fR in the string \fIstr\fR.  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.
.\" COMMAND: tcl_wordBreakBefore
.TP
\fBtcl_wordBreakBefore \fIstr start\fR
.
Returns the index of the first word boundary before the starting index
\fIstart\fR in the string \fIstr\fR.  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.
.SS "FILE ACCESS HELPERS"
.\" COMMAND: foreachLine
.TP
\fBforeachLine \fIvarName filename body\fR
.VS TIP670
This reads in the text file named \fIfilename\fR one line at a time
(using system defaults for reading text files). It writes that line to the
variable named by \fIvarName\fR and then executes \fIbody\fR for that line.
The result value of \fIbody\fR is ignored, but \fBerror\fR, \fBreturn\fR,
\fBbreak\fR and \fBcontinue\fR may be used within it to produce an error,
return from the calling context, stop the loop, or go to the next line
respectively.
The overall result of \fBforeachLine\fR is the empty string (assuming no
errors from I/O or from evaluating the body of the loop); the file will be
closed prior to the procedure returning.
.VE TIP670
.\" COMMAND: readFile
.TP
\fBreadFile \fIfilename\fR ?\fBtext\fR|\fBbinary\fR?
.VS TIP670
Reads in the file named in \fIfilename\fR and returns its contents.
The second argument says how to read in the file, either as \fBtext\fR
(using the system defaults for reading text files) or as \fBbinary\fR
(as uninterpreted bytes). The default is \fBtext\fR. When read as text, this
will include any trailing newline.
The file will be closed prior to the procedure returning.
.VE TIP670
.\" COMMAND: writeFile
.TP
\fBwriteFile \fIfilename\fR ?\fBtext\fR|\fBbinary\fR? \fIcontents\fR
.VS TIP670
Writes the \fIcontents\fR to the file named in \fIfilename\fR.
The optional second argument says how to write to the file, either as
\fBtext\fR (using the system defaults for writing text files) or as
\fBbinary\fR (as uninterpreted bytes). The default is \fBtext\fR.
If a trailing newline is required, it will need to be provided in
\fIcontents\fR. The result of this command is the empty string; the file will
be closed prior to the procedure returning.
.VE TIP670
.SH "VARIABLES"
.PP
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.
.SS "AUTOLOADING AND PACKAGE MANAGEMENT VARIABLES"
.\" VARIABLE: auto_execs
.TP
\fBauto_execs\fR
.
Used by \fBauto_execok\fR to record information about whether
particular commands exist as executable files.
.RS
.PP
Not normally usefully accessed directly by user code.
.RE
.\" VARIABLE: auto_index
.TP
\fBauto_index\fR
.
Used by \fBauto_load\fR to save the index information read from
disk.
.RS
.PP
Not normally usefully accessed directly by user code.
.RE
.\" VARIABLE: auto_noexec
.TP
\fBauto_noexec\fR
.
If set to any value, then \fBunknown\fR will not attempt to auto-exec
any commands.
.\" VARIABLE: auto_noload
.TP
\fBauto_noload\fR
.
If set to any value, then \fBunknown\fR will not attempt to auto-load
any commands.
.\" VARIABLE: env(TCL_LIBRARY)
.TP
\fBenv(TCL_LIBRARY)\fR
.
If set, then it specifies the location of the directory containing
library scripts (the value of this variable will be
assigned to the \fBtcl_library\fR variable and therefore returned by
the command \fBinfo library\fR).  If this variable is not set then
a default value is used.
.RS
.PP
Use of this environment variable is not recommended outside of testing.
Tcl installations should already know where to find their own script
files, as the value is baked in during the build or installation.
.RE
.\" VARIABLE: env(TCLLIBPATH)
.TP
\fBenv(TCLLIBPATH)\fR
.
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
.QW /
as the path separator, regardless of platform.
This variable is only used when initializing the \fBauto_path\fR variable
(see the \fBauto_load\fR command).
.RS
.PP
A key consequence of this variable is that it gives a way to let the user
of a script specify the list of places where that script may use
\fBpackage require\fR to read packages from. It is not normally usefully
settable within a Tcl script itself \fIexcept\fR to influence where other
interpreters load from (whether made with \fBinterp create\fR or launched
as their own threads or subprocesses).
.RE
.SS "WORD BOUNDARY DETERMINATION VARIABLES"
These variables are only used in the \fBtcl_endOfWord\fR,
\fBtcl_startOfNextWord\fR, \fBtcl_startOfPreviousWord\fR,
\fBtcl_wordBreakAfter\fR, and \fBtcl_wordBreakBefore\fR commands.
.\" VARIABLE: tcl_nonwordchars
.TP
\fBtcl_nonwordchars\fR
.
This variable contains a regular expression that is used by routines
like \fBtcl_endOfWord\fR 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.  The default value is \fB\eW\fR.
.\" VARIABLE: tcl_wordchars
.TP
\fBtcl_wordchars\fR
.
This variable contains a regular expression that is used by routines
like \fBtcl_endOfWord\fR 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.  The default value is \fB\ew\fR.
.SH "SEE ALSO"
env(n), info(n), re_syntax(n)
.SH KEYWORDS
auto-exec, auto-load, library, unknown, word, whitespace
'\"Local Variables:
'\"mode: nroff
'\"End:
