LIBC(7) manual page
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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 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
(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. Since this switch
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 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 dietlibc and musl libc Details
of these libraries are covered by the man-pages project, where they are
known.
syscalls(2)
, getauxval(3)
, proc(5)
, feature_test_macros(7)
,
man-pages(7)
, standards(7)
, vdso(7)
This page is part of release
3.78 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 http://www.kernel.org/doc/man-pages/.
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