Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
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.Dd August 9, 2011 .Dt UNISTD 3 .Os .Sh NAME .Nm unistd .Nd standard symbolic constants and types .Sh SYNOPSIS n unistd.h .Sh DESCRIPTION The n unistd.h header forms the basis of the Portable Operating System Interface for Unix
q Tn POSIX
.Tn API .
It includes definitions for numerous functions, symbolic constants, and types.
Among these are:
l -bullet -offset indent t The implementation-defined
.Dv NULL
pointer constant.
t Types such as
.Vt size_t ,
.Vt ssize_t ,
.Vt pid_t ,
and
.Vt intptr_t .
t Various limits and other symbolic constants described in
.Xr pathconf 2
and
.Xr sysconf 3 .
t Prototypes for several important system calls and library routines such as
.Xr chown 2 ,
.Xr dup 2 ,
.Xr execl 3 ,
.Xr fork 2 ,
.Xr pipe 2 ,
.Xr rmdir 2 ,
.Xr setuid 2 ,
and
.Xr write 2 .
t The symbolic constant
.Dv _POSIX_VERSION
that defines the version of the
.Tn POSIX
standard to which the implementation conforms.
t Various other
.Dv _POSIX
-prefixed symbolic constants that indicate whether
the system implements some optional part of the standard.
Examples include such constants as
.Dv _POSIX_IPV6
for
.Xr inet6 4
functionality and
.Dv _POSIX_ASYNCHRONOUS_IO
for
.Xr aio 3 .
.El
.Sh SEE ALSO
.Xr limits 3 ,
.Xr stddef 3 ,
.Xr stdint 3 ,
.Xr stdlib 3 ,
.Xr types 3
.Sh STANDARDS
The
n unistd.h header conforms to
.St -p1003.1-2001 .
XXX: fill this.
.Sh HISTORY
A
.In unistd.h
header first appeared in
???