libc(7)
NAME
libc - overview of standard C libraries on Linux
DESCRIPTION
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.
SEE ALSO
syscalls(2), getauxval(3), proc(5), feature_test_macros(7), man- pages(7), standards(7), vdso(7)
COLOPHON
This page is part of release 4.09 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 https://www.kernel.org/doc/man-pages/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
