libc(7) — Linux manual page


libc(7)             Miscellaneous Information 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.

       By far the most widely used C library on Linux is the GNU C
       Library ⟨⟩, 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/ (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  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

       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

SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                        libc(7)

Pages that refer to this page: syscalls(2)intro(3)feature_test_macros(7)standards(7)