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diff --git a/doc/package.n b/doc/package.n new file mode 100644 index 0000000..6cf8991 --- /dev/null +++ b/doc/package.n @@ -0,0 +1,370 @@ +'\" +'\" 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. +'\" +.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\fR ?\fIpackage package ...\fR? +\fBpackage ifneeded \fIpackage version\fR ?\fIscript\fR? +\fBpackage names\fR +\fBpackage present \fIpackage \fR?\fIrequirement...\fR? +\fBpackage present \-exact \fIpackage version\fR +\fBpackage provide \fIpackage \fR?\fIversion\fR? +\fBpackage require \fIpackage \fR?\fIrequirement...\fR? +\fBpackage require \-exact \fIpackage version\fR +\fBpackage unknown \fR?\fIcommand\fR? +\fBpackage vcompare \fIversion1 version2\fR +\fBpackage versions \fIpackage\fR +\fBpackage vsatisfies \fIversion requirement...\fR +\fBpackage prefer \fR?\fBlatest\fR|\fBstable\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\fR ?\fIpackage package ...\fR? +. +Removes all information about each specified package 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 present\fR ?\fB\-exact\fR? \fIpackage\fR ?\fIrequirement...\fR? +. +This command is equivalent to \fBpackage require\fR except that it +does not try and load the package if it is not already loaded. +.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\fIpackage \fR?\fIrequirement...\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. +.RS +.PP +A suitable version of the package is any version which satisfies at +least one of the requirements, per the rules of \fBpackage +vsatisfies\fR. If multiple versions are suitable the implementation +with the highest version is chosen. This last part is additionally +influenced by the selection mode set with \fBpackage prefer\fR. +.PP +In the +.QW stable +selection mode the command will select the highest +stable version satisfying the requirements, if any. If no stable +version satisfies the requirements, the highest unstable version +satisfying the requirements will be selected. In the +.QW latest +selection mode the command will accept the highest version satisfying +all the requirements, regardless of its stableness. +.PP +If a version of \fIpackage\fR has already been provided (by invoking +the \fBpackage provide\fR command), then its version number must +satisfy the \fIrequirement\fRs 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 evaluated +in the global namespace; +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 evaluated in the +global namespace; 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. +.RE +.TP +\fBpackage require \-exact \fIpackage version\fR +. +This form of the command is used when only the given \fIversion\fR +of \fIpackage\fR is acceptable to the caller. This command is +equivalent to \fBpackage require \fIpackage version\fR-\fIversion\fR. +.TP +\fBpackage unknown \fR?\fIcommand\fR? +. +This command supplies a +.QW "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 one or more additional arguments giving the desired +package name and requirements. +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 requirements are supplied to the \fBpackage require\fR command, +then only the name will be added to invoked command. +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 \fIversion2\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 \fIversion requirement...\fR +. +Returns 1 if the \fIversion\fR satisfies at least one of the given +requirements, and 0 otherwise. Each \fIrequirement\fR is allowed to +have any of the forms: +.RS +.TP +min +. +This form is called +.QW min-bounded . +.TP +min- +. +This form is called +.QW min-unbound . +.TP +min-max +. +This form is called +.QW bounded . +.RE +.RS +.PP +where +.QW min +and +.QW max +are valid version numbers. The legacy syntax is +a special case of the extended syntax, keeping backward +compatibility. Regarding satisfaction the rules are: +.RE +.RS +.IP [1] +The \fIversion\fR has to pass at least one of the listed +\fIrequirement\fRs to be satisfactory. +.IP [2] +A version satisfies a +.QW bounded +requirement when +.RS +.IP [a] +For \fImin\fR equal to the \fImax\fR if, and only if the \fIversion\fR +is equal to the \fImin\fR. +.IP [b] +Otherwise if, and only if the \fIversion\fR is greater than or equal +to the \fImin\fR, and less than the \fImax\fR, where both \fImin\fR +and \fImax\fR have been padded internally with +.QW a0 . +Note that while the comparison to \fImin\fR is inclusive, the +comparison to \fImax\fR is exclusive. +.RE +.IP [3] +A +.QW min-bounded +requirement is a +.QW bounded +requirement in disguise, +with the \fImax\fR part implicitly specified as the next higher major +version number of the \fImin\fR part. A version satisfies it per the +rules above. +.IP [4] +A \fIversion\fR satisfies a +.QW min-unbound +requirement if, and only if it is greater than or equal to the +\fImin\fR, where the \fImin\fR has been padded internally with +.QW a0 . +There is no constraint to a maximum. +.RE +.TP +\fBpackage prefer \fR?\fBlatest\fR|\fBstable\fR? +With no arguments, the commands returns either +.QW latest +or +.QW stable , +whichever describes the current mode of selection logic used by +\fBpackage require\fR. +.RS +.PP +When passed the argument +.QW latest , +it sets the selection logic mode to +.QW latest . +.PP +When passed the argument +.QW stable , +if the mode is already +.QW stable , +that value is kept. If the mode is already +.QW latest , +then the attempt to set it back to +.QW stable +is ineffective and the mode value remains +.QW latest . +.PP +When passed any other value as an argument, raise an invalid argument +error. +.PP +When an interpreter is created, its initial selection mode value is set to +.QW stable +unless the environment variable \fBTCL_PKG_PREFER_LATEST\fR +is set. If that environment variable is defined (with any value) then +the initial (and permanent) selection mode value is set to +.QW latest . +.RE +.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. +In addition, the letters +.QW a +(alpha) and/or +.QW b +(beta) may appear +exactly once to replace a dot for separation. These letters +semantically add a negative specifier into the version, where +.QW a +is \-2, and +.QW b +is \-1. Each may be specified only once, and +.QW a +or +.QW b +are mutually exclusive in a specifier. Thus 1.3a1 becomes (semantically) +1.3.\-2.1, 1.3b1 is 1.3.\-1.1. Negative numbers are not directly allowed +in version specifiers. +A version number not containing the letters +.QW a +or +.QW b +as specified +above is called a \fBstable\fR version, whereas presence of the letters +causes the version to be called is \fBunstable\fR. +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 have done this, packages will be loaded automatically +in response to \fBpackage require\fR commands. +See the documentation for \fBpkg_mkIndex\fR for details. +.SH EXAMPLES +.PP +To state that a Tcl script requires the Tk and http packages, put this +at the top of the script: +.PP +.CS +\fBpackage require\fR Tk +\fBpackage require\fR http +.CE +.PP +To test to see if the Snack package is available and load if it is +(often useful for optional enhancements to programs where the loss of +the functionality is not critical) do this: +.PP +.CS +if {[catch {\fBpackage require\fR Snack}]} { + # Error thrown - package not found. + # Set up a dummy interface to work around the absence +} else { + # We have the package, configure the app to use it +} +.CE +.SH "SEE ALSO" +msgcat(n), packagens(n), pkgMkIndex(n) +.SH KEYWORDS +package, version +'\" Local Variables: +'\" mode: nroff +'\" End: |