NAME | DESCRIPTION | SEE ALSO | COLOPHON

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

NAME         top

       libc - overview of standard C libraries on Linux

DESCRIPTION         top

       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 dis‐
       tributions.  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 develop‐
       ment 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 sup‐
       port the ELF binary format; this version used the shared library son‐
       ame 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 con‐
       fusion 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.  Neverthe‐
       less, 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 uClibchttp://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         top

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

COLOPHON         top

       This page is part of release 4.10 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)

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