NAME
access - determine accessibility of file

SYNOPSIS
#include <sys/file.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 */

accessible = access(path, mode)
int accessible;
const char *path;
int mode;

DESCRIPTION
Access checks the given file path for accessibility according 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.

[EINVAL] The pathname contains a character with the high-
order bit set.

[ENAMETOOLONG] A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 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.

[EROFS] Write access is requested for a file on a read-only
file system.

[ETXTBSY] Write access is requested for a pure procedure
(shared text) file that is being executed.

[EACCES] Permission bits of the file mode do not permit the
requested 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 execute 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 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)