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<?xml version='1.0'?>
<!DOCTYPE sconsdoc [
<!ENTITY % scons SYSTEM "../scons.mod">
%scons;
<!ENTITY % builders-mod SYSTEM "../generated/builders.mod">
%builders-mod;
<!ENTITY % functions-mod SYSTEM "../generated/functions.mod">
%functions-mod;
<!ENTITY % tools-mod SYSTEM "../generated/tools.mod">
%tools-mod;
<!ENTITY % variables-mod SYSTEM "../generated/variables.mod">
%variables-mod;
]>
<section id="sect-parseconfig"
xmlns="http://www.scons.org/dbxsd/v1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.scons.org/dbxsd/v1.0 http://www.scons.org/dbxsd/v1.0/scons.xsd">
<title>Finding Installed Library Information: the &ParseConfig; Function</title>
<!--
Copyright (c) 2001 - 2019 The SCons Foundation
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-->
<para>
Configuring the right options to build programs to work with
libraries--especially shared libraries--that are available
on POSIX systems can be very complicated.
To help this situation,
various utilies with names that end in <filename>config</filename>
return the command-line options for the GNU Compiler Collection (GCC)
that are needed to use these libraries;
for example, the command-line options
to use a library named <filename>lib</filename>
would be found by calling a utility named <filename>lib-config</filename>.
</para>
<para>
A more recent convention is that these options
are available from the generic <filename>pkg-config</filename> program,
which has common framework, error handling, and the like,
so that all the package creator has to do is provide the set of strings
for his particular package.
</para>
<para>
&SCons; construction environments have a &ParseConfig; method
that executes a <filename>*config</filename> utility
(either <filename>pkg-config</filename> or a
more specific utility)
and configures the appropriate construction variables
in the environment
based on the command-line options
returned by the specified command.
</para>
<scons_example name="parseconfig_ex1">
<file name="SConstruct" printme="1">
env = Environment()
env['CPPPATH'] = ['/lib/compat']
env.ParseConfig("pkg-config x11 --cflags --libs")
print(env['CPPPATH'])
</file>
</scons_example>
<para>
&SCons; will execute the specified command string,
parse the resultant flags,
and add the flags to the appropriate environment variables.
</para>
<!--
This is how we used to generate the screen output below, but
as of (at least) Ubuntu Karmic, the pkg-config output for x11
no longer reports back an include directory. Since this is just
for example anyway, we're just hard-coding the output.
<scons_output example="parseconfig_ex1" suffix="1">
<scons_output_command>scons -Q</scons_output_command>
</scons_output>
-->
<screen>
% <userinput>scons -Q</userinput>
['/lib/compat', '/usr/X11/include']
scons: `.' is up to date.
</screen>
<para>
In the example above, &SCons; has added the include directory to
<varname>CPPPATH</varname>.
(Depending upon what other flags are emitted by the
<filename>pkg-config</filename> command,
other variables may have been extended as well.)
</para>
<para>
Note that the options are merged with existing options using
the &MergeFlags; method,
so that each option only occurs once in the construction variable:
</para>
<scons_example name="parseconfig_ex2">
<file name="SConstruct" printme="1">
env = Environment()
env.ParseConfig("pkg-config x11 --cflags --libs")
env.ParseConfig("pkg-config x11 --cflags --libs")
print(env['CPPPATH'])
</file>
</scons_example>
<!--
This is how we used to generate the screen output below, but
as of (at least) Ubuntu Karmic, the pkg-config output for x11
no longer reports back an include directory. Since this is just
for example anyway, we're just hard-coding the output.
<scons_output example="parseconfig_ex2" suffix="1">
<scons_output_command>scons -Q</scons_output_command>
</scons_output>
-->
<screen>
% <userinput>scons -Q</userinput>
['/usr/X11/include']
scons: `.' is up to date.
</screen>
</section>
|
