'\"!  tbl | mmdoc
'\"macro stdmacro
.if n .pH g4.unistd @(#)unistd	40.7 of 10/10/89
.\" Copyright 1989 AT&T
.nr X
.if \nX=0 .ds x} unistd 4 "" "\&"
.if \nX=1 .ds x} unistd 4 ""
.if \nX=2 .ds x} unistd 4 "" "\&"
.if \nX=3 .ds x} unistd "" "" "\&"
.TH \*(x}
.SH NAME
\f4unistd\f1 \- header file for symbolic constants
.SH SYNOPSIS
.ft 4
#include <unistd.h>
.ft 1
.SH DESCRIPTION
.br
The \f4<unistd.h>\fP header file defines the symbolic constants and
structures which are not already defined or declared in some
other header. The contents of this header 
are shown below.
.P
The following symbolic constants are defined for the 
\f4access\f1 function [see \f4access\fP(2)]:
.in +3
.TS
lf4 l.
R_OK	Test for read permission            
W_OK	Test for write permission           
X_OK	Test for execute (search) permission 
F_OK	Test for existence of file              
.TE
.in -3
.P
The constants \f4F_OK\f1, \f4R_OK\f1, \f4W_OK\f1 and \f4X_OK\f1
and the expressions
\f4R_OK\||\|W_OK\f1,
\f4R_OK\||\|X_OK\f1
and
\f4R_OK\||\|W_OK\||\|X_OK\f1
all have distinct values.
.P
Declares the constant
.in +3
.TS
tab (@);
lf4 l.
NULL@null pointer
.TE
.in -3
.P
The following symbolic constants are defined for the 
\f4lockf\f1 function [see \f4lockf\fP(3C)]:
.in +3
.TS
lf4 l.
F_ULOCK	Unlock a previously locked region
F_LOCK	Lock a region for exclusive use
F_TLOCK	Test and lock a region for exclusive use
F_TEST	Test a region for other processes locks
.TE
.in -3
.P
The following symbolic constants are defined for the 
\f4lseek\f1 [see \f4lseek\fP(2)]
and
\f4fcntl\f1 [see \f4fcntl\fP(2)]
functions (they have distinct values):
.in +3
.TS
lf4 l.
SEEK_SET	Set file offset to \f2offset\f1
SEEK_CUR	Set file offset to current plus \f2offset\f1
SEEK_END	Set file offset to EOF plus \f2offset\f1
.TE
.in -3
.P
The following symbolic constants are defined (with fixed values):
.in +3
.TS
tab (@);
lf4 l.
_POSIX_VERSION@Integer value indicating version   
@of the POSIX standard                  
_XOPEN_VERSION@integer value indicating version of the XPG
@to which system is compliant
.TE
.in -3
.P
.ne 14
The following symbolic constants are defined to indicate that the
option is present:
.in +3
.TS
tab (@);
lf4 l.
_POSIX_JOB_CONTROL@T{
implementation supports job control
T}
_POSIX_SAVED_IDS@T{
the exec functions [see \f4exec\fP(2)]
save the effective user and group
T}
_POSIX_VDISABLE@T{
terminal special characters   
defined in \f4<termios.h>\fP [see termio(7)] can be  
disabled using this character 
T}
.TE
.in -3
.P
The following symbolic constants are defined for \f4sysconf\f1
[see \f4sysconf\fP(3C)]:
.in +3
.TS
lf4.
_SC_ARG_MAX
_SC_CHILD_MAX
_SC_CLK_TCK
_SC_JOB_CONTROL
_SC_NGROUPS_MAX
_SC_OPEN_MAX
_SC_PAGESIZE
_SC_PASS_MAX
_SC_SAVED_IDS
_SC_VERSION
_SC_XOPEN_VERSION
.TE
.in -3
.P
The following symbolic constants are defined for \f4pathconf\f1
[see fpathconf(3C)]:
.in +3
.TS
lf4.
_PC_CHOWN_RESTRICTED
_PC_LINK_MAX
_PC_MAX_CANON
_PC_MAX_INPUT
_PC_NAME_MAX
_PC_NO_TRUNC
_PC_PATH_MAX
_PC_PIPE_BUF
_PC_VDISABLE
.TE
.in -3
.P
The following symbolic constants are defined for file streams:
.in +3
.TS
lf4 l.
STDIN_FILENO	File number of \f4stdin\fP.  It is \f40\f1.
STDOUT_FILENO	File number of \f4stout\fP.  It is \f41\f1.
STDERR_FILENO	File number of \f4stderr\fP.  It is \f42\f1.
.TE
.in -3
.P
The following pathnames are defined:
.in +3
.TS
lf4 l.
GF_PATH	Pathname of the group file.
PF_PATH	Pathname of the passwd file.
.TE
.in -3
.SH NOTES
.P
The following values for constants are defined for this release of System V:
.in +3
.TS
lf4 n.
_POSIX_VERSION	198808L
_XOPEN_VERSION	3
.TE
.in -3
.SH "SEE ALSO"
.na
\f4access\fP(2),
\f4exec\fP(2), 
\f4fcntl\fP(2),
\f4lseek\fP(2),
\f4termios\fP(2),
\f4fpathconf\fP(3C),
\f4sysconf\fP(3C),
\f4group\fP(4),
\f4passwd\fP(4),
\f4termio\fP(7).
.ad
