libc(7)                                           Miscellaneous Information Manual                                          libc(7)

       libc - overview of standard C libraries on Linux

       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 de‐
       tails  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  Sep‐
       tember 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 li‐
       brary, and executing this pathname will cause glibc to display various information about the version installed on your  sys‐

   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  sup‐
       port.   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  de‐
       tails.   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

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

Linux man-pages 6.03                                         2023-02-05                                                     libc(7)