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']) void f1() { printf("f1.c\n"); } void f2() { printf("f2.c\n"); } void f3() { printf("f3.c\n"); } &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 On a Windows system, a build of the above example would look like: scons -Q 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.

The &Library; function builds a traditional static library. If you want to be explicit about the type of library being built, you can use the synonym &StaticLibrary; function instead of &Library: StaticLibrary('foo', ['f1.c', 'f2.c', 'f3.c']) There is no functional difference between the &StaticLibrary; and &Library; functions.

If you want to build a shared library (on POSIX systems) or a DLL file (on Windows systems), you use the &SharedLibrary; function: SharedLibrary('foo', ['f1.c', 'f2.c', 'f3.c']) void f1() { printf("f1.c\n"); } void f2() { printf("f2.c\n"); } void f3() { printf("f3.c\n"); } The output on POSIX: scons -Q And the output on Windows: scons -Q Notice again that &SCons; takes care of building the output file correctly, adding the -shared option for a POSIX compilation, and the /dll option on Windows.

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', 'bar'], LIBPATH='.') int main() { printf("Hello, world!\n"); } int main() { printf("Hello, world!\n"); } int main() { printf("Hello, world!\n"); } int main() { printf("Hello, world!\n"); } 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 On a Windows system, a build of the above example would look like: scons -Q As usual, notice that &SCons; has taken care of constructing the correct command lines to link with the specified library on each system. Note also that, if you only have a single library to link with, you can specify the library name in single string, instead of a Python list, so that: Program('prog.c', LIBS='foo', LIBPATH='.') is equivalent to: Program('prog.c', LIBS=['foo'], LIBPATH='.') This is similar to the way that &SCons; handles either a string or a list to specify a single source file.

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']) int main() { printf("prog.c\n"); } 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' (Note that Python requires that the backslash separators in a Windows path name be escaped within strings.) 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 On a Windows system, a build of the above example would look like: scons -Q Note again that &SCons; has taken care of the system-specific details of creating the right command-line options.