Updated: 2021/Apr/14

UNISTD(3)                  Library Functions Manual                  UNISTD(3)

     unistd - standard symbolic constants and types

     #include <unistd.h>

     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).

     limits(3), stddef(3), stdint(3), stdlib(3), types(3)

     The <unistd.h> header conforms to IEEE Std 1003.1-2001 ("POSIX.1").

NetBSD 9.99                     August 9, 2011                     NetBSD 9.99