Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
INTRO(2)                   Linux Programmer's Manual                  INTRO(2)

NAME
       intro - Introduction to system calls

DESCRIPTION
       Section 2 of the manual describes the Linux system calls.  A system
       call is an entry point into the Linux kernel.  Usually, system calls
       are not invoked directly: instead, most system calls have corresponding
       C library wrapper functions which perform the steps required (e.g.,
       trapping to kernel mode) in order to invoke the system call.  Thus,
       making a system call looks the same as invoking a normal library
       function.

       For a list of the Linux system calls, see syscalls(2).

RETURN VALUE
       On error, most system calls return a negative error number (i.e., the
       negated value of one of the constants described in errno(3)).  The C
       library wrapper hides this detail from the caller: when a system call
       returns a negative value, the wrapper copies the absolute value into
       the errno variable, and returns -1 as the return value of the wrapper.

       The value returned by a successful system call depends on the call.
       Many system calls return 0 on success, but some can return nonzero
       values from a successful call.  The details are described in the
       individual manual pages.

       In some cases, the programmer must define a feature test macro in order
       to obtain the declaration of a system call from the header file
       specified in the man page SYNOPSIS section.  In such cases, the
       required macro is described in the man page.  For further information
       on feature test macros, see feature_test_macros(7).

CONFORMING TO
       Certain terms and abbreviations are used to indicate Unix variants and
       standards to which calls in this section conform.  See standards(7).

NOTES
   Calling Directly
       In most cases, it is unnecessary to invoke a system call directly, but
       there are times when the Standard C library does not implement a nice
       wrapper function for you.  In this case, the programmer must manually
       invoke the system call using syscall(2).  Historically, this was also
       possible using one of the _syscall macros described in _syscall(2).

   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
       _syscall(2), syscall(2), errno(3), feature_test_macros(7), standards(7)

COLOPHON
       This page is part of release 3.25 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux                             2010-02-03                          INTRO(2)

NAME | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=intro&sektion=2&manpath=SuSE+Linux%2fi386+11.3>

home | help