9.4.31 unistd.h: POSIX standard symbolic constants

 

DESCRIPTION

This file contains the required symbolic constants for a POSIX system. These include the symbolic access and seek constants:

R_OK

Test for read permission.

W_OK

Test for write permission.

X_OK

Test for execute permission.

F_OK

Test for file existence.

SEEK_SET

Set file offset to value.

SEEK_CUR

Set file offset to current plus value.

SEEK_END

Set file offset to EOF plus value.

This file defines no POSIX compile-time or execution-time constants. Additionally defined are the constants:

STDIN_FILENO

File descriptor for stdin.

STDOUT_FILENO

File descriptor for stdout.

STDERR_FILENO

File descriptor for stderr.

prototypes for OSKit-supported standard POSIX functions:

_exit

Terminate a process.

access

Check file accessibility.

close

Close a file.

lseek

Reposition read/write file offset.

read

Read from a file.

unlink

Remove directory entries.

write

Write to a file.

Additionally, prototypes for other standard POSIX functions not implemented in the OSKit are included in this file. These prototypes are included as a convenience to OS developers, so that the OSKit version of this file can be used with client OSes that do provide the additional functions.

Extended functionality.

Of the OSKit implemented routines, only _exit is considered part of the base minimal C library. The remaining functions are part of the extended POSIX environment. Refer to section 9.2 for details.