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 display 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.  Linux libc4 was the last version to use the
       a.out binary format, and the first version to provide (primitive) shared library support.  Linux  libc  5
       was  the  first  version  to  support  the ELF binary format; this version used the shared library soname
       libc.so.5.  For a while, Linux libc was the standard C library in many Linux distributions.

       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.  To avoid any  confusion  with  Linux  libc  versions,
       glibc 2.0 and later used the shared library soname libc.so.6.

       Since  the  switch  from  Linux  libc  to  glibc 2.0 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 a few 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  generally  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,
       dietlibc, and musl libc.  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  5.10  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
       https://www.kernel.org/doc/man-pages/.

Linux                                              2016-12-12                                            LIBC(7)