NAME
       pkg_mkIndex  -  Build  an  index  for automatic loading of
       packages

SYNOPSIS
       pkg_mkIndex ?-lazy? ?-load pkgPat? ?-verbose? dir ?pattern pattern ...?


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  pack-
       age  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 con-
              tain 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 pack-
              age is in the auto_path global variable or an imme-
              diate subdirectory of one  of  the  directories  in
              auto_path.   Auto_path  contains a list of directo-
              ries 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 ini-
              tializes  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.  Dif-
              ferent versions of a package may be loaded in  dif-
              ferent interpreters.


OPTIONS
       The optional switches are:

       -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.

       -load pkgPat   The  index  process will pre-load any pack-
                      ages 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.  See COMPLEX
                      CASES below.

       -verbose       Generate output during  the  indexing  pro-
                      cess.   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 ver-
       sion control:  several versions of a package can  be  made
       available  in the index files, with different applications
       using different versions based  on  package  require  com-
       mands.  In contrast, auto_mkindex does not understand ver-
       sions so it can only handle a single version of each pack-
       age.   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 initializa-
       tion  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 avail-
       able package;  these commands invoke package provide  com-
       mands  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  ver-
       sion  of  a  given package isn't 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  ini-
       tialization,  might  select  that  their  package files be
       loaded immediately upon package require instead of  delay-
       ing  the  actual  loading  to  the first use of one of the
       package's command. This is the default mode when  generat-
       ing 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 com-
       mands, 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  vari-
       ables  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 API's such  as  Tcl_PkgRequire  API  when
       loading a binary file.  For example, suppose the BLT pack-
       age 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 dependen-
       cies 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  won't 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  spec-
       ify  the  scripts first; otherwise the package loaded from
       the binary file  may  mask  the  package  defined  by  the
       scripts.
KEYWORDS
       auto-load, index, package, version
