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NAME | DESCRIPTION | SEE ALSO | COLOPHON |
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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.
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 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.
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 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 confusion 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.
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
⟨http://www.uclibc.org/⟩, dietlibc ⟨http://www.fefe.de/dietlibc/⟩,
and musl libc ⟨http://www.musl-libc.org/⟩. 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 the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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