man(1) Manual page archive

     ACCESS(2)                                               ACCESS(2)

          access - determine accessibility of file

          access(name, mode)
          char *name;

          Access checks the given file name for accessibility accord-
          ing to mode, which is 4 (read), 2 (write) or 1 (execute) or
          a combination thereof.  Specifying mode 0 tests whether the
          directories leading to the file can be searched and the file

          An appropriate error indication is returned if name cannot
          be found or if any of the desired access modes would not be
          granted.  On disallowed accesses -1 is returned and the
          error code is in errno. 0 is returned from successful tests.

          The user and group IDs with respect to which permission is
          checked are the real UID and GID of the process, so this
          call is useful to set-UID programs.

          Notice that it is only access bits that are checked.  A
          directory may be announced 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 exec will
          fail unless it is in proper format.