NAME
pkg_mkIndex - Build an index for automatic loading of
packages
SYNOPSIS
pkg_mkIndex ?-lazy? ?-load pkgPat? ?-verbose? 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 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
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.
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 |
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
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.
SEE ALSO
package(n)
KEYWORDS
auto-load, index, package, version
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