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NAME

       pkg_mkIndex - Build an index for automatic loading of packages

SYNOPSIS

       pkg_mkIndex ?options...? dir ?pattern pattern ...?
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DESCRIPTION

       Pkg_mkIndex  is  a utility procedure that is part of the standard Tcl library.  It is used
       to create index files that allow packages to be loaded automatically when package  require
       commands are executed.  To use pkg_mkIndex, follow these steps:

       [1]    Create the package(s).  Each package may consist of one or more Tcl script files or
              binary files.  Binary files must be suitable for loading with the load command with
              a single argument;  for example, if the file is test.so it must be possible to load
              this file with the command load test.so.  Each script file must contain  a  package
              provide  command  to  declare  the package and version number, and each binary file
              must contain a call to Tcl_PkgProvide.

       [2]    Create the index by invoking pkg_mkIndex.  The dir argument gives  the  name  of  a
              directory  and each pattern argument is a glob-style pattern that selects script or
              binary files in dir.  The default pattern is *.tcl and *.[info sharedlibextension].

              Pkg_mkIndex will create a file pkgIndex.tcl in dir with package  information  about
              all  the  files  given by the pattern arguments.  It does this by loading each file
              into a slave interpreter and seeing what packages and new commands appear (this  is
              why it is essential to have package provide commands or Tcl_PkgProvide calls in the
              files, as described above).  If you have a package split among scripts  and  binary
              files,  or  if  you  have  dependencies  among files, you may have to use the -load
              option or adjust the order in which pkg_mkIndex processes the files.   See  COMPLEX
              CASES below.

       [3]    Install  the  package  as  a  subdirectory  of  one of the directories given by the
              tcl_pkgPath variable.  If $tcl_pkgPath contains more than one  directory,  machine-
              dependent  packages  (e.g.,  those  that  contain  binary  shared libraries) should
              normally be installed under the first directory  and  machine-independent  packages
              (e.g.,  those  that  contain only Tcl scripts) should be installed under the second
              directory.  The subdirectory should include  the  package's  script  and/or  binary
              files  as  well as the pkgIndex.tcl file.  As long as the package is installed as a
              subdirectory of a directory in $tcl_pkgPath it will automatically be  found  during
              package require commands.

              If  you  install the package anywhere else, then you must ensure that the directory
              containing the package  is  in  the  auto_path  global  variable  or  an  immediate
              subdirectory  of one of the directories in auto_path.  Auto_path contains a list of
              directories that are searched by both the auto-loader and the  package  loader;  by
              default  it  includes  $tcl_pkgPath.   The  package  loader  also checks all of the
              subdirectories of the directories  in  auto_path.   You  can  add  a  directory  to
              auto_path  explicitly  in  your  application,  or you can add the directory to your
              TCLLIBPATH environment variable:  if this  environment  variable  is  present,  Tcl
              initializes auto_path from it during application startup.

       [4]    Once  the  above  steps  have been taken, all you need to do to use a package is to
              invoke package require.  For example, if versions 2.1, 2.3, and 3.1 of package Test
              have  been  indexed  by  pkg_mkIndex,  the  command  package require Test will make
              version 3.1 available and the command package require -exact  Test  2.1  will  make
              version  2.1  available.   There  may  be many versions of a package in the various
              index files in auto_path,  but  only  one  will  actually  be  loaded  in  a  given
              interpreter,  based  on the first call to package require.  Different versions of a
              package may be loaded in different interpreters.

OPTIONS

       The optional switches are:

       -direct        The generated index will implement  direct  loading  of  the  package  upon
                      package require.  This is the default.

       -lazy          The  generated index will manage to delay loading the package until the use
                      of one of the commands provided by  the  package,  instead  of  loading  it
                      immediately  upon  package require.  This is not compatible with the use of
                      auto_reset, and therefore its use is discouraged.

       -load pkgPat   The index process will pre-load any packages  that  exist  in  the  current
                      interpreter  and  match  pkgPat into the slave interpreter used to generate
                      the index.  The pattern match uses string match rules, but  without  making
                      case distinctions.  See COMPLEX CASES below.

       -verbose       Generate  output  during  the  indexing  process.  Output is via the tclLog
                      procedure, which by default prints to stderr.

       --             End of the flags, in case dir begins with a dash.

PACKAGES AND THE AUTO-LOADER

       The package management facilities overlap somewhat with  the  auto-loader,  in  that  both
       arrange  for  files to be loaded on-demand.  However, package management is a higher-level
       mechanism that uses the auto-loader for the last step  in  the  loading  process.   It  is
       generally  better to index a package with pkg_mkIndex rather than auto_mkindex because the
       package mechanism provides version control:  several versions of a  package  can  be  made
       available  in  the index files, with different applications using different versions based
       on package require commands.  In contrast, auto_mkindex does not understand versions so it
       can only handle a single version of each package.  It is probably not a good idea to index
       a given package with both pkg_mkIndex and auto_mkindex.  If you use pkg_mkIndex to index a
       package,  its  commands  cannot be invoked until package require has been used to select a
       version;  in contrast, packages indexed with auto_mkindex can be  used  immediately  since
       there is no version control.

HOW IT WORKS

       Pkg_mkIndex  depends on the package unknown command, the package ifneeded command, and the
       auto-loader.  The first time a package require command is  invoked,  the  package  unknown
       script  is  invoked.   This is set by Tcl initialization to a script that evaluates all of
       the pkgIndex.tcl files in the auto_path.  The pkgIndex.tcl files contain package  ifneeded
       commands  for  each  version  of  each  available  package;  these commands invoke package
       provide commands to announce the availability of the package, and they  setup  auto-loader
       information  to  load  the  files of the package.  If the -lazy flag was provided when the
       pkgIndex.tcl was generated, a given file of a given version of  a  given  package  is  not
       actually loaded until the first time one of its commands is invoked.  Thus, after invoking
       package require you may not see the package's commands in the interpreter, but you will be
       able to invoke the commands and they will be auto-loaded.

DIRECT LOADING

       Some  packages,  for  instance  packages which use namespaces and export commands or those
       which require special initialization, might select that  their  package  files  be  loaded
       immediately  upon  package require instead of delaying the actual loading to the first use
       of one of the package's command. This is the default  mode  when  generating  the  package
       index.  It can be overridden by specifying the -lazy argument.

COMPLEX CASES

       Most  complex  cases  of  dependencies  among scripts and binary files, and packages being
       split among scripts and binary files are handled OK.  However, you may have to adjust  the
       order  in  which files are processed by pkg_mkIndex.  These issues are described in detail
       below.

       If each script or file contains one package, and packages are only contained in one  file,
       then  things  are easy.  You simply specify all files to be indexed in any order with some
       glob patterns.

       In general, it is OK for scripts to have  dependencies  on  other  packages.   If  scripts
       contain package require commands, these are stubbed out in the interpreter used to process
       the scripts, so these do not cause problems.  If  scripts  call  into  other  packages  in
       global  code, these calls are handled by a stub unknown command.  However, if scripts make
       variable references to other package's variables in global code, these will cause  errors.
       That is also bad coding style.

       If  binary  files have dependencies on other packages, things can become tricky because it
       is not possible to stub out C-level APIs such as Tcl_PkgRequire API when loading a  binary
       file.  For example, suppose the BLT package requires Tk, and expresses this with a call to
       Tcl_PkgRequire in its Blt_Init routine.  To support this, you must run pkg_mkIndex  in  an
       interpreter  that  has  Tk loaded.  You can achieve this with the -load pkgPat option.  If
       you specify this option, pkg_mkIndex will load any packages listed by info loaded and that
       match  pkgPat into the interpreter used to process files.  In most cases this will satisfy
       the Tcl_PkgRequire calls made by binary files.

       If you are indexing two binary files and one depends on the other, you should specify  the
       one that has dependencies last.  This way the one without dependencies will get loaded and
       indexed, and then the package it provides will  be  available  when  the  second  file  is
       processed.   You  may  also  need to load the first package into the temporary interpreter
       used to create the index by using the -load flag; it will  not  hurt  to  specify  package
       patterns that are not yet loaded.

       If  you  have  a  package  that is split across scripts and a binary file, then you should
       avoid the -load flag. The problem is that if you load a package before computing the index
       it  masks  any  other files that provide part of the same package.  If you must use -load,
       then you must specify the scripts first; otherwise the package loaded from the binary file
       may mask the package defined by the scripts.

SEE ALSO

       package(3tcl)

KEYWORDS

       auto-load, index, package, version