unistd(4) — FILE FORMATS
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_OKTest for read permission.
W_OKTest for write permission.
X_OKTest for execute (search) permission.
F_OKTest for existence of file.
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.
Declares the constant
NULLnull pointer
The following symbolic constants are defined for the lockf function [see lockf(3C)]:
F_ULOCKUnlock a previously locked region.
F_LOCKLock a region for exclusive use.
F_TLOCKTest and lock a region for exclusive use.
F_TESTTest a region for other processes locks.
The following symbolic constants are defined for the lseek [see lseek(2)] and fcntl [see fcntl(2)] functions (they have distinct values):
SEEK_SETSet file offset to offset.
SEEK_CURSet file offset to current plus offset.
SEEK_ENDSet file offset to EOF plus offset.
The following symbolic constants are defined (with fixed values):
_POSIX_VERSIONInteger value indicating version of the POSIX standard.
_XOPEN_VERSIONInteger value indicating version of the XPG to which system is compliant.
The following symbolic constants are defined to indicate that the option is present:
_POSIX_JOB_CONTROLImplementation supports job control.
_POSIX_SAVED_IDSThe exec functions [see exec(2)] save the effective user and group.
_POSIX_VDISABLETerminal special characters defined in termios.h [see termio(7)] can be disabled using this character.
The following symbolic constants are defined for sysconf [see 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 |
The following symbolic constants are defined for pathconf [see 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_FILENOFile number of stdin. It is 0.
STDOUT_FILENOFile number of stout. It is 1.
STDERR_FILENOFile number of stderr. It is 2.
The following pathnames are defined:
GF_PATHPathname of the group file.
PF_PATHPathname of the passwd file.
NOTES
The following values for constants are defined for this release of System V:
_POSIX_VERSION198808L
_XOPEN_VERSION3
SEE ALSO
access(2), exec(2), fcntl(2), fpathconf(2), lseek(2), termios(2), sysconf(3C), group(4), passwd(4), termio(7)