package(n) Tcl Built-In Commands package(n)

NAME
       package - Facilities for package loading and version control

SYNOPSIS
       ppaacckkaaggee ffoorrggeett ??package package ...?
       ppaacckkaaggee iiffnneeeeddeedd package version ?script?
       ppaacckkaaggee nnaammeess
       ppaacckkaaggee pprreesseenntt ?-eexxaacctt? package ?version?
       ppaacckkaaggee pprroovviiddee package ?version?
       ppaacckkaaggee rreeqquuiirree ?-eexxaacctt? package ?version?
       ppaacckkaaggee uunnkknnoowwnn ?command?
       ppaacckkaaggee vvccoommppaarree version1 version2
       ppaacckkaaggee vveerrssiioonnss package
       ppaacckkaaggee vvssaattiissffiieess version1 version2



DESCRIPTION
       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 cor-
       rect 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 ppaacckkaaggee rreeqquuiirree and ppaacckkaaggee  pprroovviiddee  commands  are
       invoked  in  normal Tcl scripts;  the other commands are used primarily
       by system scripts that maintain the package database.

       The behavior of the ppaacckkaaggee command is determined by  its  first  argu-
       ment.  The following forms are permitted:

       ppaacckkaaggee ffoorrggeett ??package package ...?
              Removes  all  information about each specified package from this
              interpreter, including  information  provided  by  both  ppaacckkaaggee
              iiffnneeeeddeedd and ppaacckkaaggee pprroovviiddee.

       ppaacckkaaggee iiffnneeeeddeedd package version ?script?
              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  script.  The script is saved in a database for use by
              subsequent ppaacckkaaggee rreeqquuiirree commands;  typically, script sets  up
              auto-loading  for  the  commands  in  the package (or calls llooaadd
              and/or ssoouurrccee directly), then invokes ppaacckkaaggee pprroovviiddee  to  indi-
              cate  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 package and
              version, the new script  replaces  the  existing  one.   If  the
              script  argument is omitted, the current script for version ver-
              sion of package package is returned, or an empty  string  if  no
              ppaacckkaaggee  iiffnneeeeddeedd  command has been invoked for this package and
              version.

       ppaacckkaaggee nnaammeess
              Returns a list of the names of all packages in  the  interpreter
              for  which  a version has been provided (via ppaacckkaaggee pprroovviiddee) or
              for which a ppaacckkaaggee iiffnneeeeddeedd script is available.  The order  of
              elements in the list is arbitrary.

       ppaacckkaaggee pprreesseenntt ?-eexxaacctt? package ?version?
              This  command  is  equivalent  to ppaacckkaaggee rreeqquuiirree except that it
              does not try and load the package if it is not already loaded.

       ppaacckkaaggee pprroovviiddee package ?version?
              This command is invoked to  indicate  that  version  version  of
              package  package is now present in the interpreter.  It is typi-
              cally invoked once as part of an iiffnneeeeddeedd script, and  again  by
              the  package  itself when it is finally loaded.  An error occurs
              if a different version of package has been provided by a  previ-
              ous  ppaacckkaaggee  pprroovviiddee command.  If the version argument is omit-
              ted, then the command returns the version number  that  is  cur-
              rently  provided,  or an empty string if no ppaacckkaaggee pprroovviiddee com-
              mand has been invoked for package in this interpreter.

       ppaacckkaaggee rreeqquuiirree ?-eexxaacctt? package ?version?
              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 -eexxaacctt
              switch and the version argument  are  specified  then  only  the
              given  version  is acceptable.  If -eexxaacctt is omitted but version
              is specified, then versions later than version are also  accept-
              able  as long as they have the same major version number as ver-
              sion.  If both -eexxaacctt and version are omitted then  any  version
              whatsoever  is  acceptable.  If a version of package has already
              been provided (by invoking the ppaacckkaaggee  pprroovviiddee  command),  then
              its version number must satisfy the criteria given by -eexxaacctt and
              version and the command  returns  immediately.   Otherwise,  the
              command  searches the database of information provided by previ-
              ous ppaacckkaaggee iiffnneeeeddeedd 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  ppaacckkaaggee  pprroovviiddee  for  the  package.   If  the  ppaacckkaaggee
              iiffnneeeeddeedd  database does not contain an acceptable version of the
              package and a ppaacckkaaggee uunnkknnoowwnn command has been specified for the
              interpreter  then that command is evaluated in the global names-
              pace;  when it completes, Tcl checks again to see if the package
              is now provided or if there is a ppaacckkaaggee iiffnneeeeddeedd script for it.
              If all of these steps fail to provide an acceptable  version  of
              the package, then the command returns an error.

       ppaacckkaaggee uunnkknnoowwnn ?command?
              This command supplies a ``last resort'' command to invoke during
              ppaacckkaaggee rreeqquuiirree if no suitable version of a package can be found
              in  the  ppaacckkaaggee  iiffnneeeeddeedd database.  If the command argument is
              supplied, it contains the first part of  a  command;   when  the
              command is invoked during a ppaacckkaaggee rreeqquuiirree command, Tcl appends
              two additional arguments giving the  desired  package  name  and
              version.   For example, if command is ffoooo bbaarr and later the com-
              mand ppaacckkaaggee rreeqquuiirree tteesstt 22..44 is invoked, then Tcl will  execute
              the command ffoooo bbaarr tteesstt 22..44 to load the package.  If no version
              number is supplied to the ppaacckkaaggee rreeqquuiirree command, then the ver-
              sion  argument  for the invoked command will be an empty string.
              If the ppaacckkaaggee uunnkknnoowwnn command  is  invoked  without  a  command
              argument,  then  the current ppaacckkaaggee uunnkknnoowwnn script is returned,
              or an empty string if there is none.  If command is specified as
              an  empty  string,  then  the  current ppaacckkaaggee uunnkknnoowwnn script is
              removed, if there is one.

       ppaacckkaaggee vvccoommppaarree version1 version2
              Compares the two version numbers given by version1 and version2.
              Returns -1 if version1 is an earlier version than version2, 0 if
              they are equal, and 1 if version1 is later than vveerrssiioonn22.

       ppaacckkaaggee vveerrssiioonnss package
              Returns a list of all the version numbers of package  for  which
              information has been provided by ppaacckkaaggee iiffnneeeeddeedd commands.

       ppaacckkaaggee vvssaattiissffiieess version1 version2
              Returns  1  if  scripts written for version2 will work unchanged
              with version1 (i.e. version1 is equal to or  greater  than  ver-
              sion2  and they both have the same major version number), 0 oth-
              erwise.


VVEERRSSIIOONN NNUUMMBBEERRSS
       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 exam-
       ple, 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.


PPAACCKKAAGGEE IINNDDIICCEESS
       The recommended way to use packages in Tcl is to invoke ppaacckkaaggee rreeqquuiirree
       and  ppaacckkaaggee  pprroovviiddee  commands  in  scripts,  and  use  the  procedure
       ppkkggmmkkIInnddeexx to create package index  files.   Once  you've  done  this,
       packages  will  be  loaded automatically in response to ppaacckkaaggee rreeqquuiirree
       commands.  See the documentation for ppkkggmmkkIInnddeexx for details.


SEE ALSO
       msgcat(n), packagens(n), pkgMkIndex(n)


KKEEYYWWOORRDDSS
       package, version



Tcl                                   7.5                           package(n)