LIBC(7)                             Linux Programmer's Manual                             LIBC(7)



NAME
       libc - overview of standard C libraries on Linux

DESCRIPTION
       The term "libc" is commonly used as a shorthand for the "standard C library", a library of
       standard functions that can be used by all C programs (and sometimes by programs in  other
       languages).   Because  of some history (see below), use of the term "libc" to refer to the
       standard C library is somewhat ambiguous on Linux.

   glibc
       By far the most widely used C library on Linux is the GNU  C  Library  ⟨http://www.gnu.org
       /software/libc/⟩, often referred to as glibc.  This is the C library that is nowadays used
       in all major Linux distributions.  It is also the C library whose details  are  documented
       in  the  relevant  pages  of the man-pages project (primarily in Section 3 of the manual).
       Documentation of glibc is also available in the glibc manual, available  via  the  command
       info  libc.   Release  1.0  of  glibc was made in September 1992.  (There were earlier 0.x
       releases.)  The next major release of glibc was 2.0, at the beginning of 1997.

       The pathname /lib/libc.so.6 (or something similar) is normally a symbolic link that points
       to the location of the glibc library, and executing this pathname will cause glibc to dis‐
       play various information about the version installed on your system.

   Linux libc
       In the early to mid 1990s, there was for a while Linux libc, a fork of glibc  1.x  created
       by  Linux developers who felt that glibc development at the time was not sufficing for the
       needs of Linux.  Often, this library was referred to (ambiguously) as just "libc".   Linux
       libc  released  major  versions  2,  3,  4, and 5 (as well as many minor versions of those
       releases).  For a while, Linux libc was the standard C library  in  many  Linux  distribu‐
       tions.

       However,  notwithstanding  the  original motivations of the Linux libc effort, by the time
       glibc 2.0 was released (in 1997), it was clearly superior to Linux  libc,  and  all  major
       Linux  distributions  that  had  been using Linux libc soon switched back to glibc.  Since
       this switch occurred long ago, man-pages no longer  takes  care  to  document  Linux  libc
       details.  Nevertheless, the history is visible in vestiges of information about Linux libc
       that remain in some manual pages, in particular, references to libc4 and libc5.

   Other C libraries
       There are various other less widely used C libraries for Linux.  These libraries are  gen‐
       erally  smaller  than  glibc,  both  in  terms of features and memory footprint, and often
       intended for building small binaries, perhaps targeted at development for  embedded  Linux
       systems.    Among   such   libraries   are   uClibc   ⟨http://www.uclibc.org/⟩,   dietlibc
       ⟨http://www.fefe.de/dietlibc/⟩, and musl  libc  ⟨http://www.musl-libc.org/⟩.   Details  of
       these libraries are covered by the man-pages project, where they are known.

SEE ALSO
       syscalls(2),  getauxval(3),  proc(5),  feature_test_macros(7), man-pages(7), standards(7),
       vdso(7)

COLOPHON
       This page is part of release 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.



Linux                                       2014-07-08                                    LIBC(7)