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pkg_mkIndex(3tcl) Tcl Built-In Commands pkg_mkIndex(3tcl) 





NAME


pkg_mkIndex - Build an index for automatic loading of packages






SYNOPSIS


pkg_mkIndex ?options...? 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 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 child
    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:



  

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

  

  
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.

  

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

  

  
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







  

    8.3
    Tcl