intro(3) - Linux manual page (original) (raw)

intro(3) Library Functions Manual intro(3)

NAME top

   intro - introduction to library functions

DESCRIPTION top

   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)](../man7/feature%5Ftest%5Fmacros.7.html).

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.

STANDARDS top

   Certain terms and abbreviations are used to indicate UNIX variants
   and standards to which calls in this section conform.  See
   [standards(7)](../man7/standards.7.html).

NOTES top

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!

SEE ALSO top

   [intro(2)](../man2/intro.2.html), [errno(3)](../man3/errno.3.html), [capabilities(7)](../man7/capabilities.7.html), [credentials(7)](../man7/credentials.7.html), [environ(7)](../man7/environ.7.html),
   [feature_test_macros(7)](../man7/feature%5Ftest%5Fmacros.7.html), [libc(7)](../man7/libc.7.html), [math_error(7)](../man7/math%5Ferror.7.html),
   [path_resolution(7)](../man7/path%5Fresolution.7.html), [pthreads(7)](../man7/pthreads.7.html), [signal(7)](../man7/signal.7.html), [standards(7)](../man7/standards.7.html),
   [system_data_types(7)](../man7/system%5Fdata%5Ftypes.7.html)

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   This page is part of the _man-pages_ (Linux kernel and C library
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Linux man-pages 6.10 2024-05-02 intro(3)

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