libc

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 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 http://www.uclibc.org/⟩, dietlibchttp://www.fefe.de/dietlibc/⟩, and musl libchttp://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 5.06 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)