intro(3) — Linux manual page


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).

       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).

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), 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),

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                       intro(3)

Pages that refer to this page: intro(2)