libc

       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  stan-
       dard 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 distribu-
       tions.  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 sym-
       bolic link that points to the location of the glibc library,  and  exe-
       cuting  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).  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.  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  par-
       ticular, 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     <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)
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