- pkg_mkIndex - Build an index for automatic loading of packages
- pkg_mkIndex ?-lazy? ?-load pkgPat? ?-verbose? dir ?pattern pattern ...?
- -load pkgPat
- PACKAGES AND THE AUTO-LOADER
- HOW IT WORKS
- DIRECT LOADING
- COMPLEX CASES
- SEE ALSO
pkg_mkIndex - Build an index for automatic loading of packages
pkg_mkIndex ?-lazy? ?-load pkgPat? ?-verbose? dir ?pattern pattern ...?
Pkg_mkIndex is a utility procedure that is part of the standard
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:
The optional switches are:
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.
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
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.
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
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
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.
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
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
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
a given file of a given version of a given package isn't
actually loaded until the first time one of its commands
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.
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 below.
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.
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.
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
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 API's 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
Copyright © 1996 Sun Microsystems, Inc.
Copyright © 1995-1997 Roger E. Critchlow Jr.