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NAME | DESCRIPTION | STANDARDS | NOTES | SEE ALSO | COLOPHON |
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intro(3) Library Functions Manual intro(3)
intro - introduction to library functions
Section 3 of the manual describes all library functions excluding
the library functions (system call wrappers) described in Section
2, which implement system calls.
Many of the functions described in the section are part of the
Standard C Library (libc). Some functions are part of other
libraries (e.g., the math library, libm, or the real-time library,
librt) in which case the manual page will indicate the linker
option needed to link against the required library (e.g., -lm and
-lrt, respectively, for the aforementioned libraries).
In some cases, the programmer must define a feature test macro in
order to obtain the declaration of a function from the header file
specified in the man page SYNOPSIS section. (Where required,
these feature test macros must be defined before including any
header files.) In such cases, the required macro is described in
the man page. For further information on feature test macros, see
feature_test_macros(7).
Subsections
Section 3 of this manual is organized into subsections that
reflect the complex structure of the standard C library and its
many implementations:
• 3const
• 3head
• 3type
This difficult history frequently makes it a poor example to
follow in design, implementation, and presentation.
Ideally, a library for the C language is designed such that each
header file presents the interface to a coherent software module.
It provides a small number of function declarations and exposes
only data types and constants that are required for use of those
functions. Together, these are termed an API or application
program interface. Types and constants to be shared among
multiple APIs should be placed in header files that declare no
functions. This organization permits a C library module to be
documented concisely with one header file per manual page. Such
an approach improves the readability and accessibility of library
documentation, and thereby the usability of the software.
Certain terms and abbreviations are used to indicate UNIX variants
and standards to which calls in this section conform. See
standards(7).
Authors and copyright conditions
Look at the header of the manual page source for the author(s) and
copyright conditions. Note that these can be different from page
to page!
intro(2), errno(3), capabilities(7), credentials(7), environ(7),
feature_test_macros(7), libc(7), math_error(7),
path_resolution(7), pthreads(7), signal(7), standards(7),
system_data_types(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-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. 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
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 intro(3)
Pages that refer to this page: intro(2)
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HTML rendering created 2025-09-06 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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