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markom |
'\"
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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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'\" RCS: @(#) $Id: package.n,v 1.1.1.1 2002-01-16 10:25:24 markom Exp $
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'\"
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.so man.macros
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.TH package 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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package \- Facilities for package loading and version control
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.SH SYNOPSIS
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.nf
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\fBpackage forget \fIpackage\fR
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\fBpackage ifneeded \fIpackage version\fR ?\fIscript\fR?
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\fBpackage names\fR
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\fBpackage provide \fIpackage \fR?\fIversion\fR?
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\fBpackage require \fR?\fB\-exact\fR? \fIpackage \fR?\fIversion\fR?
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\fBpackage unknown \fR?\fIcommand\fR?
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\fBpackage vcompare \fIversion1 version2\fR
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\fBpackage versions \fIpackage\fR
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\fBpackage vsatisfies \fIversion1 version2\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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This command keeps a simple database of the packages available for
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use by the current interpreter and how to load them into the
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interpreter.
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It supports multiple versions of each package and arranges
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for the correct version of a package to be loaded based on what
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is needed by the application.
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This command also detects and reports version clashes.
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Typically, only the \fBpackage require\fR and \fBpackage provide\fR
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commands are invoked in normal Tcl scripts; the other commands are used
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primarily by system scripts that maintain the package database.
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.PP
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The behavior of the \fBpackage\fR command is determined by its first argument.
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The following forms are permitted:
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.TP
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\fBpackage forget \fIpackage\fR
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Removes all information about \fIpackage\fR from this interpreter,
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including information provided by both \fBpackage ifneeded\fR and
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\fBpackage provide\fR.
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.TP
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\fBpackage ifneeded \fIpackage version\fR ?\fIscript\fR?
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This command typically appears only in system configuration
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scripts to set up the package database.
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It indicates that a particular version of
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a particular package is available if needed, and that the package
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can be added to the interpreter by executing \fIscript\fR.
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The script is saved in a database for use by subsequent
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\fBpackage require\fR commands; typically, \fIscript\fR
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sets up auto-loading for the commands in the package (or calls
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\fBload\fR and/or \fBsource\fR directly), then invokes
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\fBpackage provide\fR to indicate that the package is present.
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There may be information in the database for several different
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versions of a single package.
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If the database already contains information for \fIpackage\fR
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and \fIversion\fR, the new \fIscript\fR replaces the existing
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one.
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If the \fIscript\fR argument is omitted, the current script for
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version \fIversion\fR of package \fIpackage\fR is returned,
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or an empty string if no \fBpackage ifneeded\fR command has
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been invoked for this \fIpackage\fR and \fIversion\fR.
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.TP
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\fBpackage names\fR
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Returns a list of the names of all packages in the
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interpreter for which a version has been provided (via
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\fBpackage provide\fR) or for which a \fBpackage ifneeded\fR
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script is available.
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The order of elements in the list is arbitrary.
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.TP
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\fBpackage provide \fIpackage \fR?\fIversion\fR?
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This command is invoked to indicate that version \fIversion\fR
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of package \fIpackage\fR is now present in the interpreter.
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It is typically invoked once as part of an \fBifneeded\fR script,
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and again by the package itself when it is finally loaded.
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An error occurs if a different version of \fIpackage\fR has been
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provided by a previous \fBpackage provide\fR command.
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If the \fIversion\fR argument is omitted, then the command
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returns the version number that is currently provided, or an
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empty string if no \fBpackage provide\fR command has been
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invoked for \fIpackage\fR in this interpreter.
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.TP
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\fBpackage require \fR?\fB\-exact\fR? \fIpackage \fR?\fIversion\fR?
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This command is typically invoked by Tcl code that wishes to use
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a particular version of a particular package. The arguments
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indicate which package is wanted, and the command ensures that
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a suitable version of the package is loaded into the interpreter.
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If the command succeeds, it returns the version number that is
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loaded; otherwise it generates an error.
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If both the \fB\-exact\fR
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switch and the \fIversion\fR argument are specified then only the
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given version is acceptable. If \fB\-exact\fR is omitted but
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\fIversion\fR is specified, then versions later than \fIversion\fR
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are also acceptable as long as they have the same major version
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number as \fIversion\fR.
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If both \fB\-exact\fR and \fIversion\fR are omitted then any
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version whatsoever is acceptable.
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If a version of \fIpackage\fR has already been provided (by invoking
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the \fBpackage provide\fR command), then its version number must
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satisfy the criteria given by \fB\-exact\fR and \fIversion\fR and
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the command returns immediately.
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Otherwise, the command searches the database of information provided by
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previous \fBpackage ifneeded\fR commands to see if an acceptable
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version of the package is available.
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If so, the script for the highest acceptable version number is invoked;
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it must do whatever is necessary to load the package,
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including calling \fBpackage provide\fR for the package.
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If the \fBpackage ifneeded\fR database does not contain an acceptable
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version of the package and a \fBpackage unknown\fR command has been
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specified for the interpreter then that command is invoked; when
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it completes, Tcl checks again to see if the package is now provided
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or if there is a \fBpackage ifneeded\fR script for it.
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If all of these steps fail to provide an acceptable version of the
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package, then the command returns an error.
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.TP
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\fBpackage unknown \fR?\fIcommand\fR?
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This command supplies a ``last resort'' command to invoke during
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\fBpackage require\fR if no suitable version of a package can be found
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in the \fBpackage ifneeded\fR database.
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If the \fIcommand\fR argument is supplied, it contains the first part
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of a command; when the command is invoked during a \fBpackage require\fR
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command, Tcl appends two additional arguments giving the desired package
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name and version.
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For example, if \fIcommand\fR is \fBfoo bar\fR and later the command
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\fBpackage require test 2.4\fR is invoked, then Tcl will execute
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the command \fBfoo bar test 2.4\fR to load the package.
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If no version number is supplied to the \fBpackage require\fR command,
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then the version argument for the invoked command will be an empty string.
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If the \fBpackage unknown\fR command is invoked without a \fIcommand\fR
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argument, then the current \fBpackage unknown\fR script is returned,
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or an empty string if there is none.
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If \fIcommand\fR is specified as an empty string, then the current
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\fBpackage unknown\fR script is removed, if there is one.
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.TP
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\fBpackage vcompare \fIversion1 version2\fR
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Compares the two version numbers given by \fIversion1\fR and \fIversion2\fR.
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Returns -1 if \fIversion1\fR is an earlier version than \fIversion2\fR,
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.TP
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\fBpackage versions \fIpackage\fR
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Returns a list of all the version numbers of \fIpackage\fR
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for which information has been provided by \fBpackage ifneeded\fR
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commands.
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.TP
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\fBpackage vsatisfies \fIversion1 version2\fR
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Returns 1 if scripts written for \fIversion2\fR will work unchanged
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with \fIversion1\fR (i.e. \fIversion1\fR is equal to or greater
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than \fIversion2\fR and they both have the same major version
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number), 0 otherwise.
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.SH "VERSION NUMBERS"
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.PP
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Version numbers consist of one or more decimal numbers separated
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by dots, such as 2 or 1.162 or 3.1.13.1.
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The first number is called the major version number.
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Larger numbers correspond to later versions of a package, with
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leftmost numbers having greater significance.
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For example, version 2.1 is later than 1.3 and version
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3.4.6 is later than 3.3.5.
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Missing fields are equivalent to zeroes: version 1.3 is the
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same as version 1.3.0 and 1.3.0.0, so it is earlier than 1.3.1 or 1.3.0.2.
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A later version number is assumed to be upwards compatible with
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an earlier version number as long as both versions have the same
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major version number.
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For example, Tcl scripts written for version 2.3 of a package should
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work unchanged under versions 2.3.2, 2.4, and 2.5.1.
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Changes in the major version number signify incompatible changes:
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if code is written to use version 2.1 of a package, it is not guaranteed
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to work unmodified with either version 1.7.3 or version 3.1.
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.SH "PACKAGE INDICES"
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.PP
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The recommended way to use packages in Tcl is to invoke \fBpackage require\fR
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and \fBpackage provide\fR commands in scripts, and use the procedure
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\fBpkg_mkIndex\fR to create package index files.
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Once you've done this, packages will be loaded automatically
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in response to \fBpackage require\fR commands.
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See the documentation for \fBpkg_mkIndex\fR for details.
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.SH KEYWORDS
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package, version
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