4.3BSD-UWisc/man/cat2/access.2

ACCESS(2)           UNIX Programmer's Manual            ACCESS(2)



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;
     char *path;
     int mode;

DESCRIPTION
     _A_c_c_e_s_s checks the given file _p_a_t_h for accessibility accord-
     ing to _m_o_d_e, which is an inclusive or of the bits R_OK, W_OK
     and X_OK.  Specifying _m_o_d_e 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 _a_c_c_e_s_s, but an attempt to open
     it for writing will fail (although files may be created
     there); a file may look executable, but _e_x_e_c_v_e will fail
     unless it is in proper format.

RETURN VALUE
     If _p_a_t_h 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 char-
                    acters, or an entire path name exceeded 1023
                    characters.




Printed 12/27/86          May 22, 1986                          1






ACCESS(2)           UNIX Programmer's Manual            ACCESS(2)



     [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 pro-
                    cedure (shared text) file that is being exe-
                    cuted.

     [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]       _P_a_t_h 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)




















Printed 12/27/86          May 22, 1986                          2