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+'\"
+'\" Copyright (c) 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.
+'\" 
+'\" RCS: @(#) $Id$
+'\" 
+.so man.macros
+.TH package n 7.5 Tcl "Tcl Built-In Commands"
+.BS
+'\" Note:  do not modify the .SH NAME line immediately below!
+.SH NAME
+package \- Facilities for package loading and version control
+.SH SYNOPSIS
+.nf
+\fBpackage forget \fIpackage\fR
+\fBpackage ifneeded \fIpackage version\fR ?\fIscript\fR?
+\fBpackage names\fR
+\fBpackage provide \fIpackage \fR?\fIversion\fR?
+\fBpackage require \fR?\fB\-exact\fR? \fIpackage \fR?\fIversion\fR?
+\fBpackage unknown \fR?\fIcommand\fR?
+\fBpackage vcompare \fIversion1 version2\fR
+\fBpackage versions \fIpackage\fR
+\fBpackage vsatisfies \fIversion1 version2\fR
+.fi
+.BE
+
+.SH DESCRIPTION
+.PP
+This command keeps a simple database of the packages available for
+use by the current interpreter and how to load them into the
+interpreter.
+It supports multiple versions of each package and arranges
+for the correct version of a package to be loaded based on what
+is needed by the application.
+This command also detects and reports version clashes.
+Typically, only the \fBpackage require\fR and \fBpackage provide\fR
+commands are invoked in normal Tcl scripts;  the other commands are used
+primarily by system scripts that maintain the package database.
+.PP
+The behavior of the \fBpackage\fR command is determined by its first argument.
+The following forms are permitted:
+.TP
+\fBpackage forget \fIpackage\fR
+Removes all information about \fIpackage\fR from this interpreter,
+including information provided by both \fBpackage ifneeded\fR and
+\fBpackage provide\fR.
+.TP
+\fBpackage ifneeded \fIpackage version\fR ?\fIscript\fR?
+This command typically appears only in system configuration
+scripts to set up the package database.
+It indicates that a particular version of
+a particular package is available if needed, and that the package
+can be added to the interpreter by executing \fIscript\fR.
+The script is saved in a database for use by subsequent
+\fBpackage require\fR commands;  typically, \fIscript\fR
+sets up auto-loading for the commands in the package (or calls
+\fBload\fR and/or \fBsource\fR directly), then invokes
+\fBpackage provide\fR to indicate that the package is present.
+There may be information in the database for several different
+versions of a single package.
+If the database already contains information for \fIpackage\fR
+and \fIversion\fR, the new \fIscript\fR replaces the existing
+one.
+If the \fIscript\fR argument is omitted, the current script for
+version \fIversion\fR of package \fIpackage\fR is returned,
+or an empty string if no \fBpackage ifneeded\fR command has
+been invoked for this \fIpackage\fR and \fIversion\fR.
+.TP
+\fBpackage names\fR
+Returns a list of the names of all packages in the
+interpreter for which a version has been provided (via
+\fBpackage provide\fR) or for which a \fBpackage ifneeded\fR
+script is available.
+The order of elements in the list is arbitrary.
+.TP
+\fBpackage provide \fIpackage \fR?\fIversion\fR?
+This command is invoked to indicate that version \fIversion\fR
+of package \fIpackage\fR is now present in the interpreter.
+It is typically invoked once as part of an \fBifneeded\fR script,
+and again by the package itself when it is finally loaded.
+An error occurs if a different version of \fIpackage\fR has been
+provided by a previous \fBpackage provide\fR command.
+If the \fIversion\fR argument is omitted, then the command
+returns the version number that is currently provided, or an
+empty string if no \fBpackage provide\fR command has been
+invoked for \fIpackage\fR in this interpreter.
+.TP
+\fBpackage require \fR?\fB\-exact\fR? \fIpackage \fR?\fIversion\fR?
+This command is typically invoked by Tcl code that wishes to use
+a particular version of a particular package.  The arguments
+indicate which package is wanted, and the command ensures that
+a suitable version of the package is loaded into the interpreter.
+If the command succeeds, it returns the version number that is
+loaded;  otherwise it generates an error.
+If both the \fB\-exact\fR
+switch and the \fIversion\fR argument are specified then only the
+given version is acceptable.  If \fB\-exact\fR is omitted but
+\fIversion\fR is specified, then versions later than \fIversion\fR
+are also acceptable as long as they have the same major version
+number as \fIversion\fR.
+If both \fB\-exact\fR and \fIversion\fR are omitted then any
+version whatsoever is acceptable.
+If a version of \fIpackage\fR has already been provided (by invoking
+the \fBpackage provide\fR command), then its version number must
+satisfy the criteria given by \fB\-exact\fR and \fIversion\fR and
+the command returns immediately.
+Otherwise, the command searches the database of information provided by
+previous \fBpackage ifneeded\fR commands to see if an acceptable
+version of the package is available.
+If so, the script for the highest acceptable version number is invoked;
+it must do whatever is necessary to load the package,
+including calling \fBpackage provide\fR for the package.
+If the \fBpackage ifneeded\fR database does not contain an acceptable
+version of the package and a \fBpackage unknown\fR command has been
+specified for the interpreter then that command is invoked;  when
+it completes, Tcl checks again to see if the package is now provided
+or if there is a \fBpackage ifneeded\fR script for it.
+If all of these steps fail to provide an acceptable version of the
+package, then the command returns an error.
+.TP
+\fBpackage unknown \fR?\fIcommand\fR?
+This command supplies a ``last resort'' command to invoke during
+\fBpackage require\fR if no suitable version of a package can be found
+in the \fBpackage ifneeded\fR database.
+If the \fIcommand\fR argument is supplied, it contains the first part
+of a command;  when the command is invoked during a \fBpackage require\fR
+command, Tcl appends two additional arguments giving the desired package
+name and version.
+For example, if \fIcommand\fR is \fBfoo bar\fR and later the command
+\fBpackage require test 2.4\fR is invoked, then Tcl will execute
+the command \fBfoo bar test 2.4\fR to load the package.
+If no version number is supplied to the \fBpackage require\fR command,
+then the version argument for the invoked command will be an empty string.
+If the \fBpackage unknown\fR command is invoked without a \fIcommand\fR
+argument, then the current \fBpackage unknown\fR script is returned,
+or an empty string if there is none.
+If \fIcommand\fR is specified as an empty string, then the current
+\fBpackage unknown\fR script is removed, if there is one.
+.TP
+\fBpackage vcompare \fIversion1 version2\fR
+Compares the two version numbers given by \fIversion1\fR and \fIversion2\fR.
+Returns -1 if \fIversion1\fR is an earlier version than \fIversion2\fR,
+0 if they are equal, and 1 if \fIversion1\fR is later than \fBversion2\fR.
+.TP
+\fBpackage versions \fIpackage\fR
+Returns a list of all the version numbers of \fIpackage\fR
+for which information has been provided by \fBpackage ifneeded\fR
+commands.
+.TP
+\fBpackage vsatisfies \fIversion1 version2\fR
+Returns 1 if scripts written for \fIversion2\fR will work unchanged
+with \fIversion1\fR (i.e. \fIversion1\fR is equal to or greater
+than \fIversion2\fR and they both have the same major version
+number), 0 otherwise.
+
+.SH "VERSION NUMBERS"
+.PP
+Version numbers consist of one or more decimal numbers separated
+by dots, such as 2 or 1.162 or 3.1.13.1.
+The first number is called the major version number.
+Larger numbers correspond to later versions of a package, with
+leftmost numbers having greater significance.
+For example, version 2.1 is later than 1.3 and version
+3.4.6 is later than 3.3.5.
+Missing fields are equivalent to zeroes:  version 1.3 is the
+same as version 1.3.0 and 1.3.0.0, so it is earlier than 1.3.1 or 1.3.0.2.
+A later version number is assumed to be upwards compatible with
+an earlier version number as long as both versions have the same
+major version number.
+For example, Tcl scripts written for version 2.3 of a package should
+work unchanged under versions 2.3.2, 2.4, and 2.5.1.
+Changes in the major version number signify incompatible changes:
+if code is written to use version 2.1 of a package, it is not guaranteed
+to work unmodified with either version 1.7.3 or version 3.1.
+
+.SH "PACKAGE INDICES"
+.PP
+The recommended way to use packages in Tcl is to invoke \fBpackage require\fR
+and \fBpackage provide\fR commands in scripts, and use the procedure
+\fBpkg_mkIndex\fR to create package index files.
+Once you've done this, packages will be loaded automatically
+in response to \fBpackage require\fR commands.
+See the documentation for \fBpkg_mkIndex\fR for details.
+
+.SH KEYWORDS
+package, version