ACCESS(2) BSD Programmer's Manual ACCESS(2)
access - check access permissions of a file or pathname
access(const char *path, int mode);
The access() function checks the accessibility of the file named by path
for the access permissions indicated by mode. The value of mode is the
bitwise inclusive OR of the access permissions to be checked (R_OK for
read permission, W_OK for write permission and X_OK for execute/search
permission) or the existence test, F_OK. All components of the pathname
path are checked for access permissions (including F_OK).
The real user ID is used in place of the effective user ID and the real
group access list (including the real group ID) are used in place of the
effective ID for verifying permission.
Even if a process has appropriate privileges and indicates success for
X_OK, the file may not actually have execute permission bits set. Like-
wise for R_OK and W_OK.
If path cannot be found or if any of the desired access modes would not
be granted, then a -1 value is returned; otherwise a 0 value is returned.
Access to the file is denied if:
[ENOTDIR] A component of the path prefix is not a directory.
[EINVAL] The pathname contains a character with the high-order bit
A component of a pathname exceeded 255 characters, or an
entire path name exceeded 1023 characters.
[ENOENT] The named file does not exist.
[ELOOP] Too many symbolic links were encountered in translating the
[EROFS] Write access is requested for a file on a read-only file
[ETXTBSY] Write access is requested for a pure procedure (shared
text) file presently being executed.
[EACCES] Permission bits of the file mode do not permit the request-
ed access, or search permission is denied on a component of
the path prefix. The owner of a file has permission
checked with respect to the ``owner'' read, write, and exe-
cute mode bits, members of the file's group other than the
owner have permission checked with respect to the ``group''
mode bits, and all others have permissions checked with re-
spect to the ``other'' mode bits.
[EFAULT] Path points outside the process's allocated address space.
[EIO] An I/O error occurred while reading from or writing to the
Access() conforms to IEEE Std 1003.1-1988 (``POSIX'').
Access() is a potential security hole and should never be used.
4th Berkeley Distribution April 1, 1994 2