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 <para>

 &SCons; has a bewildering array of construction variables
 for different types of options when building programs.
 Sometimes you may not know exactly which variable
 should be used for a particular option.

 </para>

 <para>

 &SCons; construction environments have a &ParseFlags; method
 that takes a set of typical command-line options
 and distrbutes them into the appropriate construction variables.
 Historically, it was created to support the &ParseConfig; method,
 so it focuses on options used by the GNU Compiler Collection (GCC)
 for the C and C++ toolchains.

 </para>

 <para>

 &ParseFlags; returns a dictionary containing the options
 distributed into their respective construction variables.
 Normally, this dictionary would be passed to &MergeFlags;
 to merge the options into a &consenv;,
 but the dictionary can be edited if desired to provide
 additional functionality.
 (Note that if the flags are not going to be edited,
 calling &MergeFlags; with the options directly
 will avoid an additional step.)

 </para>

 <programlisting>
    env = Environment()
    d = env.ParseFlags("-I/opt/include -L/opt/lib -lfoo")
    for k,v in sorted(d.items()):
        if v:
            print k, v
    env.MergeFlags(d)
    env.Program('f1.c')
 </programlisting>

 <screen>
    % <userinput>scons -Q</userinput>
    CPPPATH ['/opt/include']
    LIBPATH ['/opt/lib']
    LIBS ['foo']
    cc -o f1.o -c -I/opt/include f1.c
    cc -o f1 f1.o -L/opt/lib -lfoo
 </screen>

 <para>

 Note that if the options are limited to generic types
 like those above,
 they will be correctly translated for other platform types:

 </para>

 <screen>
    C:\><userinput>scons -Q</userinput>
    CPPPATH ['/opt/include']
    LIBPATH ['/opt/lib']
    LIBS ['foo']
    cl /Fof1.obj /c f1.c /nologo /I\opt\include
    link /nologo /OUT:f1.exe /LIBPATH:\opt\lib foo.lib f1.obj
    embedManifestExeCheck(target, source, env)
 </screen>

 <para>

 Since the assumption is that the flags are used for the GCC toolchain,
 unrecognized flags are placed in &cv-link-CCFLAGS;
 so they will be used for both C and C++ compiles:

 </para>

 <programlisting>
    env = Environment()
    d = env.ParseFlags("-whatever")
    for k,v in sorted(d.items()):
        if v:
            print k, v
    env.MergeFlags(d)
    env.Program('f1.c')
 </programlisting>

 <screen>
    % <userinput>scons -Q</userinput>
    CCFLAGS -whatever
    cc -o f1.o -c -whatever f1.c
    cc -o f1 f1.o
 </screen>

 <para>

 &ParseFlags; will also accept a (recursive) list of strings as input;
 the list is flattened before the strings are processed:

 </para>

 <programlisting>
    env = Environment()
    d = env.ParseFlags(["-I/opt/include", ["-L/opt/lib", "-lfoo"]])
    for k,v in sorted(d.items()):
        if v:
            print k, v
    env.MergeFlags(d)
    env.Program('f1.c')
 </programlisting>

 <screen>
    % <userinput>scons -Q</userinput>
    CPPPATH ['/opt/include']
    LIBPATH ['/opt/lib']
    LIBS ['foo']
    cc -o f1.o -c -I/opt/include f1.c
    cc -o f1 f1.o -L/opt/lib -lfoo
 </screen>

 <para>

 If a string begins with a "!" (an exclamation mark, often called a bang),
 the string is passed to the shell for execution.
 The output of the command is then parsed:

 </para>

 <programlisting>
    env = Environment()
    d = env.ParseFlags(["!echo -I/opt/include", "!echo -L/opt/lib", "-lfoo"])
    for k,v in sorted(d.items()):
        if v:
            print k, v
    env.MergeFlags(d)
    env.Program('f1.c')
 </programlisting>

 <screen>
    % <userinput>scons -Q</userinput>
    CPPPATH ['/opt/include']
    LIBPATH ['/opt/lib']
    LIBS ['foo']
    cc -o f1.o -c -I/opt/include f1.c
    cc -o f1 f1.o -L/opt/lib -lfoo
 </screen>

 <para>

 &ParseFlags; is regularly updated for new options;
 consult the man page for details about those currently recognized.

 </para>
