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116 lines
5.1 KiB
Plaintext
116 lines
5.1 KiB
Plaintext
'\"
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'\" Copyright (c) 1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) pkgMkIndex.n 1.2 96/02/15 20:03:23
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'\"
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.so man.macros
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.TH pkg_mkIndex n 7.5 Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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pkg_mkIndex \- Build an index for automatic loading of packages
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.SH SYNOPSIS
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.nf
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\fBpkg_mkIndex \fIdir \fIpattern \fR?\fIpattern pattern ...\fR?
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.fi
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.BE
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.SH DESCRIPTION
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.PP
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\fBPkg_mkIndex\fR is a utility procedure that is part of the standard
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Tcl library.
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It is used to create index files that allow packages to be loaded
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automatically when \fBpackage require\fR commands are executed.
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To use \fBpkg_mkIndex\fR, follow these steps:
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.IP [1]
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Create the package(s).
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Each package may consist of one or more Tcl script files or binary files.
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Binary files must be suitable for loading with the \fBload\fR command
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with a single argument; for example, if the file is \fBtest.so\fR it must
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be possible to load this file with the command \fBload test.so\fR.
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Each script file must contain a \fBpackage provide\fR command to declare
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the package and version number, and each binary file must contain
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a call to \fBTcl_PkgProvide\fR.
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.IP [2]
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Create the index by invoking \fBpkg_mkIndex\fR.
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The \fIdir\fR argument gives the name of a directory and each
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\fIpattern\fR argument is a \fBglob\fR-style pattern that selects
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script or binary files in \fIdir\fR.
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\fBPkg_mkIndex\fR will create a file \fBpkgIndex.tcl\fR in \fIdir\fR
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with package information about all the files given by the \fIpattern\fR
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arguments.
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It does this by loading each file and seeing what packages
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and new commands appear (this is why it is essential to have
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\fBpackage provide\fR commands or \fBTcl_PkgProvide\fR calls
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in the files, as described above).
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.IP [3]
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Make sure that the directory is in the \fBauto_path\fR global variable.
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\fBAuto_path\fR contains a list of directories that are searched
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by both the auto-loader and the package loader.
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If you want access to files described by a \fBpkgIndex.tcl\fR file
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in a directory, that directory must be present in \fBauto_path\fR.
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You can add the directory to \fBauto_path\fR explicitly in your
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application, or you can add the directory to your \fBTCLLIBPATH\fR
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environment variable: if this environment variable is present,
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Tcl initializes \fBauto_path\fR from it during application startup.
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.IP [4]
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Once the above steps have been taken, all you need to do to use a
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package is to invoke \fBpackage require\fR.
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For example, if versions 2.1, 2.3, and 3.1 of package \fBTest\fR
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have been indexed by \fBpkg_mkIndex\fR, the command
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\fBpackage require Test\fR will make vesion 3.1 available
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and the command \fBpackage require \-exact Test 2.1\fR will
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make version 2.1 available.
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There may be many versions of a package in the various index files
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in \fBauto_path\fR, but only one will actually be loaded in a given
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interpreter, based on the first call to \fBpackage require\fR.
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Different versions of a package may be loaded in different
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interpreters.
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.SH "PACKAGES AND THE AUTO-LOADER"
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.PP
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The package management facilities overlap somewhat with the auto-loader,
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in that both arrange for files to be loaded on-demand.
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However, package management is a higher-level mechanism that uses
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the auto-loader for the last step in the loading process.
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It is generally better to index a package with \fBpkg_mkIndex\fR
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rather than \fBauto_mkindex\fR because the package mechanism provides
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version control: several versions of a package can be made available
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in the index files, with different applications using different
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versions based on \fBpackage require\fR commands.
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In contrast, \fBauto_mkindex\fR does not understand versions so
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it can only handle a single version of each package.
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It is probably not a good idea to index a given package with both
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\fBpkg_mkIndex\fR and \fBauto_mkindex\fR.
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If you use \fBpkg_mkIndex\fR to index a package, its commands cannot
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be invoked until \fBpackage require\fR has been used to select a
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version; in contrast, packages indexed with \fBauto_mkindex\fR
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can be used immediately since there is no version control.
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.SH "HOW IT WORKS"
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.PP
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\fBPkg_mkIndex\fR depends on the \fBpackage unknown\fR command,
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the \fBpackage ifneeded\fR command, and the auto-loader.
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The first time a \fBpackage require\fR command is invoked,
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the \fBpackage unknown\fR script is invoked.
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This is set by Tcl initialization to a script that
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evaluates all of the \fBpkgIndex.tcl\fR files in the
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\fBauto_path\fR.
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The \fBpkgIndex.tcl\fR files contain \fBpackage ifneeded\fR
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commands for each version of each available package; these commands
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invoke \fBpackage provide\fR commands to announce the
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availability of the package, and they setup auto-loader
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information to load the files of the package.
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A given file of a given version of a given package isn't
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actually loaded until the first time one of its commands
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is invoked.
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Thus, after invoking \fBpackage require\fR you won't see
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the package's commands in the interpreter, but you will be able
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to invoke the commands and they will be auto-loaded.
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.SH KEYWORDS
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auto-load, index, package, version
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