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<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>
<programlisting>
env = Environment()
env['CPPPATH'] = ['/lib/compat']
env.ParseConfig("pkg-config x11 --cflags --libs")
print env['CPPPATH']
</programlisting>
<para>
&SCons; will execute the specified command string,
parse the resultant flags,
and add the flags to the appropriate environment variables.
</para>
<screen>
% <userinput>scons -Q</userinput>
Package x11 was not found in the pkg-config search path.
Perhaps you should add the directory containing `x11.pc'
to the PKG_CONFIG_PATH environment variable
No package 'x11' found
OSError: 'pkg-config x11 --cflags --libs' exited 1:
File "/home/my/project/SConstruct", line 3:
env.ParseConfig("pkg-config x11 --cflags --libs")
File "bootstrap/src/engine/SCons/Environment.py", line 1474:
None
File "bootstrap/src/engine/SCons/Environment.py", line 593:
None
</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>
<programlisting>
env = Environment()
env.ParseConfig("pkg-config x11 --cflags --libs")
env.ParseConfig("pkg-config x11 --cflags --libs")
print env['CPPPATH']
</programlisting>
<screen>
% <userinput>scons -Q</userinput>
Package x11 was not found in the pkg-config search path.
Perhaps you should add the directory containing `x11.pc'
to the PKG_CONFIG_PATH environment variable
No package 'x11' found
OSError: 'pkg-config x11 --cflags --libs' exited 1:
File "/home/my/project/SConstruct", line 2:
env.ParseConfig("pkg-config x11 --cflags --libs")
File "bootstrap/src/engine/SCons/Environment.py", line 1474:
None
File "bootstrap/src/engine/SCons/Environment.py", line 593:
None
</screen>
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