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
NULLpointer 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_VERSIONthat 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_IPV6for inet6(4) functionality and_POSIX_ASYNCHRONOUS_IOfor aio(3).
SEE ALSO
STANDARDS
The <unistd.h>
header conforms to IEEE Std 1003.1-2001
(“POSIX.1”).