It's often useful to organize large software projects by collecting parts of the software into one or more libraries. &SCons; makes it easy to create libraries and to use them in the programs.

You build your own libraries by specifying &Library; instead of &Program;: Library('foo', ['f1.c', 'f2.c', 'f3.c']) &SCons; uses the appropriate library prefix and suffix for your system. So on POSIX or Linux systems, the above example would build as follows (although &ranlib; may not be called on all systems): % scons -Q cc -c -o f1.o f1.c cc -c -o f2.o f2.c cc -c -o f3.o f3.c ar r libfoo.a f1.o f2.o f3.o ranlib libfoo.a On a Windows system, a build of the above example would look like: C:\>scons -Q cl /nologo /c f1.c /Fof1.obj cl /nologo /c f2.c /Fof2.obj cl /nologo /c f3.c /Fof3.obj lib /nologo /OUT:foo.lib f1.obj f2.obj f3.obj The rules for the target name of the library are similar to those for programs: if you don't explicitly specify a target library name, &SCons; will deduce one from the name of the first source file specified, and &SCons; will add an appropriate file prefix and suffix if you leave them off.

Usually, you build a library because you want to link it with one or more programs. You link libraries with a program by specifying the libraries in the &LIBS; construction variable, and by specifying the directory in which the library will be found in the &LIBPATH; construction variable: Library('foo', ['f1.c', 'f2.c', 'f3.c']) Program('prog.c', LIBS='foo', LIBPATH='.') Notice, of course, that you don't need to specify a library prefix (like lib) or suffix (like .a or .lib). &SCons; uses the correct prefix or suffix for the current system. On a POSIX or Linux system, a build of the above example would look like: % scons -Q cc -c -o f1.o f1.c cc -c -o f2.o f2.c cc -c -o f3.o f3.c ar r libfoo.a f1.o f2.o f3.o ranlib libfoo.a cc -c -o prog.o prog.c cc -o prog prog.o -L. -lfoo On a Windows system, a build of the above example would look like: C:\>scons -Q cl /nologo /c f1.c /Fof1.obj cl /nologo /c f2.c /Fof2.obj cl /nologo /c f3.c /Fof3.obj lib /nologo /OUT:foo.lib f1.obj f2.obj f3.obj cl /nologo /c prog.c /Foprog.obj link /nologo /OUT:prog.exe /LIBPATH:. foo.lib prog.obj As usual, notice that &SCons; has taken care of constructing the correct command lines to link with the specified library on each system.

By default, the linker will only look in certain system-defined directories for libraries. &SCons; knows how to look for libraries in directories that you specify with the &LIBPATH; construction variable. &LIBPATH; consists of a list of directory names, like so: Program('prog.c', LIBS = 'm', LIBPATH = ['/usr/lib', '/usr/local/lib']) Using a Python list is preferred because it's portable across systems. Alternatively, you could put all of the directory names in a single string, separated by the system-specific path separator character: a colon on POSIX systems: LIBPATH = '/usr/lib:/usr/local/lib' or a semi-colon on Windows systems: LIBPATH = 'C:\lib;D:\lib' When the linker is executed, &SCons; will create appropriate flags so that the linker will look for libraries in the same directories as &SCons;. So on a POSIX or Linux system, a build of the above example would look like: % scons -Q cc -c -o prog.o prog.c cc -o prog prog.o -L/usr/lib -L/usr/local/lib -lm On a Windows system, a build of the above example would look like: C:\>scons -Q cl /nologo /c prog.c /Foprog.obj link /nologo /OUT:prog.exe /LIBPATH:\usr\lib /LIBPATH:\usr\local\lib m.lib prog.obj Note again that &SCons; has taken care of the system-specific details of creating the right command-line options.