NAME
access - determine accessibility of file
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
#define R_OK 4/* test for read permission */
#define W_OK 2/* test for write permission */
#define X_OK 1/* test for execute (search) permission */
#define F_OK 0/* test for presence of file */
int access(const char *path, mode_t mode)
DESCRIPTION
Access checks the given file path for accessibility accord-
ing to mode, which is an inclusive or of the bits R_OK, W_OK
and X_OK. Specifying mode as F_OK (i.e., 0) tests whether
the directories leading to the file can be searched and the
file exists.
The real user ID and the group access list (including the
real group ID) are used in verifying permission, so this
call is useful to set-UID programs.
Notice that only access bits are checked. A directory may
be indicated as writable by access, but an attempt to open
it for writing will fail (although files may be created
there); a file may look executable, but execve will fail
unless it is in proper format.
RETURN VALUE
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.
ERRORS
Access to the file is denied if one or more of the following
are true:
[ENOTDIR] A component of the path prefix is not a
directory.
[ENAMETOOLONG] The path name exceeds PATH_MAX characters.
[ENOENT] The named file does not exist.
[EACCES] Search permission is denied for a component
of the path prefix.
[ELOOP] Too many symbolic links were encountered in
translating the pathname. (Minix-vmd)
[EROFS] Write access is requested for a file on a
read-only file system.
[EACCES] Permission bits of the file mode do not per-
mit the requested access, or search permis-
sion 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 execute mode bits, members of the
file's group other than the owner have per-
mission checked with respect to the ``group''
mode bits, and all others have permissions
checked with respect 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 file system.
SEE ALSO
chmod(2), stat(2).