unistd(4)
NAME
unistd − header for symbolic constants
SYNOPSIS
#include <unistd.h>
DESCRIPTION
The <unistd.h> header 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.
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 |
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
| NULL | null pointer |
The following symbolic constants are defined for the lockf function [see lockf(3C)]:
| 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 [see lseek(2)] and fcntl [see 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):
| _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 constants are defined to indicate that the option is present:
| _POSIX_JOB_CONTROL | implementation supports job control |
| _POSIX_SAVED_IDS | the exec functions (see exec(2)) |
| 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 (see sysconf(3C)):
| _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 |
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_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:
| _POSIX_VERSION | 199009L |
| _XOPEN_VERSION | 3 |
SEE ALSO
access(2), exec(2), fcntl(2), fpathconf(2), lseek(2), termios(3), sysconf(3C), group(4), passwd(4), termio(7)
Sun Microsystems — Last change: 3 Jul 1990