ACCESS - see if a file can be accessed.

(Compatible with UNIX System V C)

Usage:

#include <fildes.h>
ret = access( name, mode );

Where:

char *name;: points to a string containing the name of the file to be checked.
int mode;: indicates what sort of accessibility is to be determined. If "mode" is 0, "access" checks for the file's existence. If "mode" is 1, "access" checks if the current program can execute the file. If "mode" is 2, "access" checks if the current program can write on the file. If "mode" is 4, "access" checks if the current program can read the file.
int ret;: is zero if the access is permitted. Otherwise a -1 is returned and the library variable "errno" is set to indicate the error (see below).

Description:

"access" determines if the current program can access a particular file.

Possible Errors:

errno=ENOENT: The file or pathname was not found. This can also mean that "name" was a null string.
errno=EACCES: access denied. You do not have permission to access the file in the requested way.
errno=FMScode: "access" can also set "errno" to an FMS error code indicating the reason for the error.

Notes:

"access" is an attempt to emulate the UNIX "access" system call. Since the file systems are different, this emulation cannot be perfect. In particular, an attempt to "fopen" a file may be denied even if "access" says the file exists and has permissions.

UNIX users will note that this version of "access" requires inclusion of <fildes.h>. A different #include file is needed on UNIX.

On GCOS, "errno" will reflect the FMS status. Also, if "mode" is zero, "access" returns zero only if the FMS status definitely indicates that the file exists. There are conceivable situations where it could be argued that a "file" "existed" but "access" returns -1.