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Updated: Wednesday, February 10, 2021
 
 

package (1t)

Name

package - Facilities for package loading and version control

Synopsis

package forget ?package package ...?
package ifneeded package version ?script?
package names
package present package ?requirement...?
package present -exact package version
package provide package ?version?
package require package ?requirement...?
package require -exact package version
package unknown ?command?
package vcompare version1 version2
package versions package
package vsatisfies version requirement...
package prefer ?latest|stable?

Description

package(1t)                  Tcl Built-In Commands                 package(1t)



______________________________________________________________________________

NAME
       package - Facilities for package loading and version control

SYNOPSIS
       package forget ?package package ...?
       package ifneeded package version ?script?
       package names
       package present package ?requirement...?
       package present -exact package version
       package provide package ?version?
       package require package ?requirement...?
       package require -exact package version
       package unknown ?command?
       package vcompare version1 version2
       package versions package
       package vsatisfies version requirement...
       package prefer ?latest|stable?
______________________________________________________________________________

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 package require and package  provide  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 package command is determined by  its  first  argu-
       ment.  The following forms are permitted:

       package forget ?package package ...?
              Removes  all  information about each specified package from this
              interpreter, including  information  provided  by  both  package
              ifneeded and package provide.

       package ifneeded 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 package require commands;  typically, script sets  up
              auto-loading  for  the  commands  in  the package (or calls load
              and/or source directly), then invokes package provide  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
              package  ifneeded  command has been invoked for this package and
              version.

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

       package present ?-exact? package ?requirement...?
              This  command  is  equivalent  to package require except that it
              does not try and load the package if it is not already loaded.

       package provide 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 ifneeded 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  package  provide 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 package provide com-
              mand has been invoked for package in this interpreter.

       package require package ?requirement...?
              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.

              A suitable version of the package is any version which satisfies
              at least one of the requirements, per the rules of package vsat-
              isfies.  If  multiple  versions  are suitable the implementation
              with the highest version is chosen. This last part is  addition-
              ally influenced by the selection mode set with package prefer.

              In the "stable" selection mode the command will select the high-
              est 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
              "latest" selection mode the command will accept the highest ver-
              sion satisfying all the requirements, regardless of its  stable-
              ness.

              If  a  version of package has already been provided (by invoking
              the package provide command), then its version number must  sat-
              isfy the requirements and the command returns immediately.  Oth-
              erwise, the command searches the database  of  information  pro-
              vided by previous package ifneeded commands to see if an accept-
              able 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 package provide for the package.  If the pack-
              age ifneeded database does not contain an acceptable version  of
              the package and a package unknown 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 package ifneeded script
              for  it.   If  all  of these steps fail to provide an acceptable
              version of the package, then the command returns an error.

       package require -exact package version
              This form of the command is used when only the given version  of
              package is acceptable to the caller.  This command is equivalent
              to package require package version-version.

       package unknown ?command?
              This command supplies a "last resort" command to  invoke  during
              package require if no suitable version of a package can be found
              in the package ifneeded database.  If the  command  argument  is
              supplied,  it  contains  the  first part of a command;  when the
              command is invoked during a package require command, Tcl appends
              one or more additional arguments giving the desired package name
              and requirements.  For example, if command is foo bar and  later
              the  command  package require test 2.4 is invoked, then Tcl will
              execute the command foo bar test 2.4 to load the package.  If no
              requirements  are  supplied to the package require command, then
              only the name will be added to invoked command.  If the  package
              unknown  command is invoked without a command argument, then the
              current package unknown script is returned, or an  empty  string
              if  there  is none.  If command is specified as an empty string,
              then the current package unknown script is removed, if there  is
              one.

       package vcompare 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 version2.

       package versions package
              Returns  a  list of all the version numbers of package for which
              information has been provided by package ifneeded commands.

       package vsatisfies version requirement...
              Returns 1 if the version satisfies at least  one  of  the  given
              requirements,  and  0  otherwise. Each requirement is allowed to
              have any of the forms:

              min    This form is called "min-bounded".

              min-   This form is called "min-unbound".

              min-max
                     This form is called "bounded".

              where "min" and "max" are valid version numbers. The legacy syn-
              tax  is  a special case of the extended syntax, keeping backward
              compatibility. Regarding satisfaction the rules are:

              [1]    The version has to  pass  at  least  one  of  the  listed
                     requirements to be satisfactory.

              [2]    A version satisfies a "bounded" requirement when

                     [a]    For  min equal to the max if, and only if the ver-
                            sion is equal to the min.

                     [b]    Otherwise if, and only if the version  is  greater
                            than  or  equal to the min, and less than the max,
                            where both min and max have been padded internally
                            with  "a0".  Note that while the comparison to min
                            is inclusive, the comparison to max is exclusive.

              [3]    A "min-bounded" requirement is a "bounded" requirement in
                     disguise,  with  the max part implicitly specified as the
                     next higher major version number of the min part. A  ver-
                     sion satisfies it per the rules above.

              [4]    A  version  satisfies a "min-unbound" requirement if, and
                     only if it is greater than or equal to the min, where the
                     min  has  been  padded internally with "a0".  There is no
                     constraint to a maximum.

       package prefer ?latest|stable?
              With no arguments, the commands returns either "latest" or "sta-
              ble",  whichever  describes  the current mode of selection logic
              used by package require.

              When passed the argument "latest", it sets the  selection  logic
              mode to "latest".

              When  passed the argument "stable", if the mode is already "sta-
              ble", that value is kept.  If the mode is already "latest", then
              the  attempt  to  set it back to "stable" is ineffective and the
              mode value remains "latest".

              When passed any other value as an  argument,  raise  an  invalid
              argument error.

              When an interpreter is created, its initial selection mode value
              is set to "stable" unless the environment variable  TCL_PKG_PRE-
              FER_LATEST  is  set.   If  that  environment variable is defined
              (with any value) then the initial (and permanent) selection mode
              value is set to "latest".

VERSION NUMBERS
       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.  In addition, the letters "a" (alpha) and/or  "b"  (beta)  may
       appear  exactly  once  to  replace  a dot for separation. These letters
       semantically add a negative specifier into the version,  where  "a"  is
       -2,  and "b" is -1. Each may be specified only once, and "a" or "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 "a"
       or  "b" as specified above is called a stable version, whereas presence
       of the letters causes the version to be called is  unstable.   A  later
       version number is assumed to be upwards compatible with an earlier ver-
       sion number as long as both versions have the same major  version  num-
       ber.   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 writ-
       ten 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.

PACKAGE INDICES
       The recommended way to use packages in Tcl is to invoke package require
       and  package  provide  commands  in  scripts,  and  use  the  procedure
       pkg_mkIndex  to  create  package index files.  Once you have done this,
       packages will be loaded automatically in response  to  package  require
       commands.  See the documentation for pkg_mkIndex for details.

EXAMPLES
       To  state that a Tcl script requires the Tk and http packages, put this
       at the top of the script:

              package require Tk
              package require http

       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:

              if {[catch {package require 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
              }


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | runtime/tcl-8    |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+
SEE ALSO
       msgcat(n), packagens(n), pkgMkIndex(n)

KEYWORDS
       package, version



NOTES
       This    software    was    built    from    source     available     at
       https://github.com/oracle/solaris-userland.    The  original  community
       source was downloaded from  http://prdownloads.sourceforge.net/tcl/tcl-
       core8.6.7-src.tar.gz

       Further information about this software can be found on the open source
       community website at https://www.tcl.tk/.



Tcl                                   7.5                          package(1t)