Chapter 10. Finding Installed Library Information: the ParseConfig Function

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 config 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 lib would be found by calling a utility named lib-config.

A more recent convention is that these options are available from the generic pkg-config 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.

SCons construction environments have a ParseConfig method that executes a *config utility (either pkg-config 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.

    env = Environment()
    env['CPPPATH'] = ['/lib/compat']
    env.ParseConfig("pkg-config x11 --cflags --libs")
    print env['CPPPATH']
 

SCons will execute the specified command string, parse the resultant flags, and add the flags to the appropriate environment variables.

    % scons -Q
    ['/lib/compat', '/usr/X11/include']
    scons: `.' is up to date.
 

In the example above, SCons has added the include directory to CPPPATH. (Depending upon what other flags are emitted by the pkg-config command, other variables may have been extended as well.)

Note that the options are merged with existing options using the MergeFlags method, so that each option only occurs once in the construction variable:

    env = Environment()
    env.ParseConfig("pkg-config x11 --cflags --libs")
    env.ParseConfig("pkg-config x11 --cflags --libs")
    print env['CPPPATH']
 

    % scons -Q
    ['/usr/X11/include']
    scons: `.' is up to date.