NAME
unistd —
standard symbolic constants
and types
SYNOPSIS
#include <unistd.h>
DESCRIPTION
The
<unistd.h> header forms the basis
of the Portable Operating System Interface for Unix (POSIX) API. It includes
definitions for numerous functions, symbolic constants, and types. Among these
are:
- The implementation-defined
NULL
pointer constant.
- Types such as size_t,
ssize_t, pid_t, and
intptr_t.
- Various limits and other symbolic constants described in
pathconf(2) and
sysconf(3).
- Prototypes for several important system calls and
library routines such as
chown(2),
dup(2),
execl(3),
fork(2),
pipe(2),
rmdir(2),
setuid(2), and
write(2).
- The symbolic constant
_POSIX_VERSION
that defines the version of the
POSIX standard to which the implementation conforms.
- Various other
_POSIX
-prefixed
symbolic constants that indicate whether the system implements some
optional part of the standard. Examples include such constants as
_POSIX_IPV6
for
inet6(4) functionality and
_POSIX_ASYNCHRONOUS_IO
for
aio(3).
SEE ALSO
limits(3),
stddef(3),
stdint(3),
stdlib(3),
types(3)
STANDARDS
The
<unistd.h> header conforms to
IEEE Std 1003.1-2001 (“POSIX.1”).