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       pkg_mkIndex - Build an index for automatic loading of packages


       pkg_mkIndex ?-direct?  ?-lazy?  ?-load pkgPat? ?-verbose? dir ?pattern pattern ...?        │


       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 it must be possible to load
              this file with the command load  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.


       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.

       -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.


       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.


       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 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  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.


       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

       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 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 specify the scripts first; otherwise the package loaded from the binary file
       may mask the package defined by the scripts.




       auto-load, index, package, version