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 (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.
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, 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 over a decade 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 particular,
references to libc4 and libc5.)
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/) and dietlibc (http://www.fefe.de/dietlibc/). Details of these
libraries are generally not covered by the man-pages project.
This page is part of release 3.33 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at http://man7.org/linux/man-pages/.
|
Copyright (c) 2009 Linux Foundation, written by Michael Kerrisk <mtk.manpagesgmail.com> Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. |