unistd(5)

NAME

unistd: unistd.h — standard structures and symbolic constants

SYNOPSIS

#include <unistd.h>

DESCRIPTION

The header <unistd.h> defines the following structures and symbolic constants:

Symbolic constants for the access() 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.

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.

Symbolic constant representing a null pointer:

NULL

Symbolic constants for the lseek() and fcntl() functions (the following constants 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".

Symbolic constants (with fixed values):

_POSIX_VERSION: Integer value indicating version of IEEE Std 1003.1 standard implemented. The current value is 199009L, indicating the (4-digit) year and (2-digit) month that the standard was approved by the IEEE Standards Board. However, if any of the symbols _AES_SOURCE, _XPG3, or _POSIX1_1988 is defined before <unistd.h> is included, the value of this symbol will be 198808L.
_POSIX2_VERSION: Integer value indicating version of IEEE Std1003.2 standard implemented. The current value is 199209L, indicating the (4-digit) year and (2-digit) month that the standard was approved by the IEEE Standards Board.
_POSIX2_C_VERSION: Integer value indicating version of IEEE Std 1003.2 C-Language Binding Option implemented. The current value is 199209L, indicating the (4-digit) year and (2-digit) month that the standard was approved by the IEEE Standards Board.
_XOPEN_VERSION: Integer value indicating issue number of the X/Open Portability Guide implemented. The current value is 4, indicating Issue 4. However, if the symbol _XPG3 is defined before <unistd.h> is included, the value of this symbol will be 3.

The following symbolic constants are defined in this header if the state of the corresponding option or restriction does not vary after compilation. If a symbol is absent from this header, the value or presence of the corresponding option or restriction should be determined at execution time through sysconf() or pathconf():

_POSIX_CHOWN_RESTRICTED: The use of chown() is restricted to processes that have appropriate privileges.
_POSIX_JOB_CONTROL: Implementation supports job control (true of all HP-UX implementations).
_POSIX_NO_TRUNC: Pathname components longer than NAME_MAX generate an error.
_POSIX_REALTIME_SIGNALS: Implementation supports Realtime Signals Extensions (true of all HP-UX implementations).
_POSIX_SAVED_IDS: Effective user and group are saved across an exec() call (true of all HP-UX implementations).
_POSIX_FSYNC: Implementation supports File Synchronization (true of all HP-UX implementations). See open(2).
_POSIX_SYNCHRONIZED_IO: Implementation supports Synchronized IO (true of all HP-UX implementations). See open(2).
_POSIX_VDISABLE: Terminal special characters can be disabled using this character (see termio(7)).
_POSIX_THREADS: Implementation supports POSIX threads.
_POSIX2_C_BIND: All POSIX.2 C-language functionality is provided in the default libraries used by the c89 C compiler (see cc(1)).
_POSIX2_LOCALEDEF: New locales can be defined by using the localedef command (see localedef(1M)).
_POSIX2_UPE: The system supports IEEE Std1003.2a (POSIX User Portability Utilities Option).
_POSIX2_CHAR_TERM: At least one terminal exists that supports all required POSIX.2a commands.

All symbolic constants whose names begin _CS, _PC, and _SC (see confstr(3C), pathconf(2), and sysconf(2)) are defined.

The following symbolic constants for file streams are defined:

STDIN_FILENO: File number of standard input (stdin).
STDOUT_FILENO: File number of standard output (stdout).
STDERR_FILENO: File number of standard error (stderr).

The types size_t, ssize_t, uid_t, gid_t, off_t, and pid_t are defined.

Declarations are provided for the following functions:

`access()`	`alarm()`	`brk()`	`chdir()`
`chown()`	`chroot()`	`close()`	`confstr()`
`crypt()`	`ctermid()`	`cuserid()`	`dup()`
`dup2()`	`encrypt()`	`endusershell()`	`execl()`
`execle()`	`execlp()`	`execv()`	`execve()`
`execvp()`	`_exit()`	`fchown()`	`fork()`
`fpathconf()`	`fsync()`	`ftruncate()`	`getcwd()`
`getegid()`	`geteuid()`	`getgid()`	`getgroups()`
`gethostname()`	`getlogin()`	`getopt()`
`getpass()`	`getpgrp()`	`getpgrp2()`	`getpid()`
`getppid()`	`getuid()`	`getusershell()`	`initgroups()`
`ioctl()`	`isatty()`	`link()`	`lockf()`
`logname()`	`lseek()`	`mkstemp()`	`mktemp()`
`nice()`	`pathconf()`	`pause()`	`pipe()`
`prealloc()`	`read()`	`readlink()`	`rmdir()`
`sbrk()`	`setgid()`	`setgroups()`	`sethostname()`
`setpgid()`	`setpgrp()`	`setpgrp2()`	`setresgid()`
`setresuid()`	`setsid()`	`setuid()`	`setusershell()`
`sgetl()`	`sleep()`	`sputl()`	`swab()`

`swapon()`	`symlink()`	`sync()`	`sysconf()`
`tcgetpgrp()`	`tcsetpgrp()`	`truncate()`	`ttyname()`
`ttyslot()`	`unlink()`	`vfork()`	`write()`

AUTHOR

unistd was developed by HP.

STANDARDS CONFORMANCE

<unistd.h>: AES, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, POSIX.2, POSIX.4

unistd(5)

Technical documentation

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