Library (computing) - File Naming

File Naming

• Most modern Unix-like systems

The system stores libfoo.a and libfoo.so files in directories such as /lib, /usr/lib or /usr/local/lib. The filenames always start with lib, and end with .a (archive, static library) or .so (shared object, dynamically linked library). Some systems might have multiple names for the dynamically linked library, with most of the names being names for symbolic links to the remaining name; those names might include the major version of the library, or the full version number; for example, on some systems libfoo.so.2 would be the filename for the second major interface revision of the dynamically linked library libfoo. The .la files sometimes found in the library directories are libtool archives, not usable by the system as such.

• Mac OS X

The system inherits static library conventions from BSD, with the library stored in a .a file, and can use .so-style dynamically linked libraries (with the .dylib suffix instead). Most libraries in Mac OS X, however, consist of "frameworks", placed inside special directories called "bundles" which wrap the library's required files and metadata. For example, a framework called MyFramework would be implemented in a bundle called MyFramework.framework, with MyFramework.framework/MyFramework being either the dynamically linked library file or being a symlink to the dynamically linked library file in MyFramework.framework/Versions/Current/MyFramework.

• Microsoft Windows

Dynamically linkable libraries usually have the suffix *.DLL, although other file name extensions may be used for specific purpose dynamically linked libraries, e.g. *.OCX for OLE libraries. The interface revisions are either encoded in the file names, or abstracted away using COM-object interfaces. Depending on how they are compiled, *.LIB files can be either static libraries or representations of dynamically linkable libraries needed only during compilation, known as "Import Libraries". Unlike in the UNIX world, where different file extensions are used, when linking against .LIB file in Windows one must first know if it is a regular static library or an import library. In the latter case, a .DLL file must be present at run time.