unistd(4) unistd(4)
NAME
unistd - header file for symbolic constants
SYNOPSIS
#include <unistd.h>
DESCRIPTION
The unistd.h header file defines the symbolic constants and
structures not already defined or declared in some other
header file. The contents of this file are shown below.
The following symbolic constants are defined for the access
function [see access(2)]:
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.
EFF_ONLY_OK Use effective ids instead of real ids.
The constants F_OK, R_OK, W_OK and X_OK and the expressions
R_OK|W_OK, R_OK|X_OK and R_OK|W_OK|X_OK all have distinct
values. EFF_ONLY_OK can be ORed with any of these.
unistd declares the constant
NULL null pointer
The following symbolic constants are defined for the lockf(3C)
function:
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.
The following symbolic constants are defined for the lseek(2)
and fcntl(2) functions (they have distinct values):
SEEK_SET Set file offset to offset.
SEEK_CUR Set file offset to current plus offset.
SEEK_END Set file offset to EOF plus offset.
The following symbolic constants are defined (with fixed
values):
Copyright 1994 Novell, Inc. Page 1
unistd(4) unistd(4)
_POSIX_VERSION Integer value indicating version
of the POSIX standard.
_XOPEN_VERSION Integer value indicating version
of the XPG to which system is
compliant.
The following symbolic constant is defined for the confstr
function:
CS_PATH Value for the PATH environment variable that
includes all the standard utilities.
The following symbolic constants are defined to indicate that
the option is present:
_POSIX_JOB_CONTROL Implementation supports job
control.
_POSIX_SAVED_IDS The exec(2) functions save the
effective user and group.
_POSIX_VDISABLE Terminal special characters
defined in termios.h [see
termio(7)] can be disabled using
this character.
The following symbolic constants are defined for sysconf(3C):
_SC_ARG_MAX
_SC_CHILD_MAX
_SC_CLK_TCK
_SC_JOB_CONTROL
_SC_LOGNAME_MAX
_SC_NGROUPS_MAX
_SC_OPEN_MAX
_SC_PAGESIZE
_SC_PASS_MAX
_SC_SAVED_IDS
_SC_VERSION
_SC_XOPEN_VERSION
_SC_TZNAME_MAX
_SC_STREAM_MAX
_SC_XOPEN_SHM
_SC_XOPEN_CRYPT
_SC_XOPEN_ENH_I18N
_SC_2_LOCALDEF
_SC_BC_BASE_MAX
_SC_BC_DIM_MAX
_SC_BC_SCALE_MAX
Copyright 1994 Novell, Inc. Page 2
unistd(4) unistd(4)
_SC_BC_STRING_MAX
_SC_COLL_WEIGHTS_MAX
_SC_EXPR_NEST_MAX
_SC_LINE_MAX
_SC_2_VERSION
_SC_RE_DUP_MAX
_SC_2_C_DEV
_SC_2_C_BIND
_SC_2_C_VERSION
_SC_2_CHAR_TERM
_SC_2_FORT_DEV
_SC_2_SW_DEV
_SC_2_UPE
The following symbolic constants are defined for fpathconf(2):
_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
The following symbolic constants are defined for file streams:
STDIN_FILENO File number of stdin. It is 0.
STDOUT_FILENO File number of stout. It is 1.
STDERR_FILENO File number of stderr. It is 2.
The following pathnames are defined:
GF_PATH Pathname of the group file.
PF_PATH Pathname of the passwd file.
REFERENCES
access(2), exec(2), fcntl(2), fork(2), fpathconf(2), group(4),
lseek(2), passwd(4), pread(2), pwrite(2), sysconf(3C),
termio(7), termios(3C)
NOTICES
The following values for constants are defined for this
release of System V:
Copyright 1994 Novell, Inc. Page 3
unistd(4) unistd(4)
_POSIX_VERSION 199009L
_XOPEN_VERSION 4
_XOPEN_ENH_I18N (-1L)
_XOPEN_XPG4 1
_POSIX2_C_VERSION (-1L)
_XOPEN_XCU_VERSION 3
Copyright 1994 Novell, Inc. Page 4