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.so man.macros

.TH pkg_mkIndex n 8.0 Tcl "Tcl Built-In Commands"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

pkg_mkIndex \- Build an index for automatic loading of packages

.SH SYNOPSIS

.nf

.VS 8.0.3

\fBpkg_mkIndex ?\fI-direct\fR? ?\fI-load pkgPat\fR? ?\fI-verbose\fR? \fIdir\fR ?\fIpattern pattern ...\fR?

.VE

.fi

.BE

.SH DESCRIPTION

.PP

\fBPkg_mkIndex\fR 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 \fBpackage require\fR commands are executed.

To use \fBpkg_mkIndex\fR, follow these steps:

.IP [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 \fBload\fR command

with a single argument;  for example, if the file is \fBtest.so\fR it must

be possible to load this file with the command \fBload test.so\fR.

Each script file must contain a \fBpackage provide\fR command to declare

the package and version number, and each binary file must contain

a call to \fBTcl_PkgProvide\fR.

.IP [2]

Create the index by invoking \fBpkg_mkIndex\fR.

The \fIdir\fR argument gives the name of a directory and each

\fIpattern\fR argument is a \fBglob\fR-style pattern that selects

script or binary files in \fIdir\fR.

.VS 8.0.3

The default pattern is \fB*.tcl\fR and \fB*.[info sharedlibextension]\fR.

The optional switches are:

.TP 15

\fB\-direct\fR

The generated index

will manage to load the package immediately upon \fBpackage require\fR

instead of delaying loading until actual use of one of the commands.

.TP 15

\fB\-load \fIpkgPat\fR

The index process will pre-load any packages that exist in the

current interpreter and match \fIpkgPat\fP into the slave interpreter used to

generate the index.  The pattern match uses string match rules.

See COMPLEX CASES below.

.TP 15

\fB\-verbose\fR

Generate output during the indexing process.  Output is via

the \fBtclLog\fP procedure, which by default prints to stderr.

.TP 15

\fB\-\-\fR

End of the flags, in case \fIdir\fP begins with a dash.

.VE

.LP

.RS

\fBPkg_mkIndex\fR will create a file \fBpkgIndex.tcl\fR in \fIdir\fR

with package information about all the files given by the \fIpattern\fR

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

\fBpackage provide\fR commands or \fBTcl_PkgProvide\fR 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 \fB-load\fP option

or adjust the order in which \fBpkg_mkIndex\fR processes

the files.  See COMPLEX CASES below.

.RE

.IP [3]

Install the package as a subdirectory of one of the directories given by

the \fBtcl_pkgPath\fR variable.  If \fB$tcl_pkgPath\fR 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 \fBpkgIndex.tcl\fR

file.  As long as the package is installed as a subdirectory of a

directory in \fB$tcl_pkgPath\fR it will automatically be found during

\fBpackage require\fR commands.

.IP

If you install the package anywhere else, then you must ensure that

the directory containing the package is in the \fBauto_path\fR global variable

or an immediate subdirectory of one of the directories in \fBauto_path\fR.

\fBAuto_path\fR contains a list of directories that are searched

by both the auto-loader and the package loader; by default it

includes \fB$tcl_pkgPath\fR.

The package loader also checks all of the subdirectories of the

directories in \fBauto_path\fR.

You can add a directory to \fBauto_path\fR explicitly in your

application, or you can add the directory to your \fBTCLLIBPATH\fR

environment variable:  if this environment variable is present,

Tcl initializes \fBauto_path\fR from it during application startup.

.IP [4]

Once the above steps have been taken, all you need to do to use a

package is to invoke \fBpackage require\fR.

For example, if versions 2.1, 2.3, and 3.1 of package \fBTest\fR

have been indexed by \fBpkg_mkIndex\fR, the command

\fBpackage require Test\fR will make version 3.1 available

and the command \fBpackage require \-exact Test 2.1\fR will

make version 2.1 available.

There may be many versions of a package in the various index files

in \fBauto_path\fR, but only one will actually be loaded in a given

interpreter, based on the first call to \fBpackage require\fR.

Different versions of a package may be loaded in different

interpreters.

.SH "PACKAGES AND THE AUTO-LOADER"

.PP

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 \fBpkg_mkIndex\fR

rather than \fBauto_mkindex\fR 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 \fBpackage require\fR commands.

In contrast, \fBauto_mkindex\fR 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

\fBpkg_mkIndex\fR and \fBauto_mkindex\fR.

If you use \fBpkg_mkIndex\fR to index a package, its commands cannot

be invoked until \fBpackage require\fR has been used to select a

version;  in contrast, packages indexed with \fBauto_mkindex\fR

can be used immediately since there is no version control.

.SH "HOW IT WORKS"

.PP

\fBPkg_mkIndex\fR depends on the \fBpackage unknown\fR command,

the \fBpackage ifneeded\fR command, and the auto-loader.

The first time a \fBpackage require\fR command is invoked,

the \fBpackage unknown\fR script is invoked.

This is set by Tcl initialization to a script that

evaluates all of the \fBpkgIndex.tcl\fR files in the

\fBauto_path\fR.

The \fBpkgIndex.tcl\fR files contain \fBpackage ifneeded\fR

commands for each version of each available package;  these commands

invoke \fBpackage provide\fR commands to announce the

availability of the package, and they setup auto-loader

information to load the files of the package.

.VS 8.0.3

Unless the \fI-direct\fR flag was provided when the \fBpkgIndex.tcl\fR

was generated,

.VE

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 \fBpackage require\fR you

.VS 8.0.3

may

.VE

not see

the package's commands in the interpreter, but you will be able

to invoke the commands and they will be auto-loaded.

.VS 8.0.3

.SH "DIRECT LOADING"

.PP

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 \fBpackage require\fR

instead of delaying the actual loading to the first use of one of the

package's command. This mode is enabled when generating the package

index by specifying the \fI-direct\fR argument.

.VE

.SH "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 \fBpkg_mkIndex\fR.

These issues are described in detail below.

.PP

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.

.PP

In general, it is OK for scripts to have dependencies on other

packages.

If scripts contain \fBpackage require\fP 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 \fBunknown\fP 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.

.PP

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 \fBTcl_PkgRequire\fP API

when loading a binary file.

For example, suppose the BLT package requires Tk, and expresses

this with a call to \fBTcl_PkgRequire\fP in its \fBBlt_Init\fP routine.

To support this, you must run \fBpkg_mkIndex\fR in an interpreter that

has Tk loaded.  You can achieve this with the

\fB-load \fIpkgPat\fR option.  If you specify this option,

\fBpkg_mkIndex\fR will load any packages listed by

\fBinfo loaded\fP and that match \fIpkgPat\fP

into the interpreter used to process files.

In most cases this will satisfy the \fBTcl_PkgRequire\fP calls

made by binary files.

.PP

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 \fB-load\fP flag;

it won't hurt to specify package patterns that are not yet loaded.

.PP

If you have a package that is split across scripts and a binary file,

then you should avoid the \fB-load\fP 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 \fB-load\fP,

then you must specify the scripts first; otherwise the package loaded from

the binary file may mask the package defined by the scripts.

.SH KEYWORDS

auto-load, index, package, version