unistd(FP)

Syntax

#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 here.

The following symbolic constants are defined for the access(S) function:

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.h declares the constant

NULL

null pointer

The following symbolic constants are defined for the lockf(S) 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(S) and fcntl(S) 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):

_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(S) 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(S) family of functions save the effective user and group.

_POSIX_VDISABLE

Terminal special characters defined in termios.h (see termio(M) and termios(M)) can be disabled using this character.

The following symbolic constants are defined for sysconf(S):

_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

_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

_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 pathconf(S):

_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.

Notes

The following values for constants are defined for this release:

_POSIX_VERSION

199009L

_XOPEN_VERSION

4

_XOPEN_ENH_I18N

(-1L)

_XOPEN_XPG4

1

See also

Standards conformance