#include <stdio.h>

     int
     rename(const char *from, const char *to)

DESCRIPTION

     Rename() causes the link named from to be renamed as to. If to exists, it
     is first removed.  Both from and to must be of the same type (that is,
     both directories or both non-directories), and must reside on the same
     file system.

     Rename() guarantees that an instance of to will always exist, even if the
     system should crash in the middle of the operation.

     If the final component of from is a symbolic link, the symbolic link is
     renamed, not the file or directory to which it points.

CAVEAT

     The system can deadlock if a loop in the file system graph is present.
     This loop takes the form of an entry in directory `a', say `a/foo', being
     a hard link to directory `b', and an entry in directory `b', say `b/bar',
     being a hard link to directory `a'. When such a loop exists and two sepa-
     rate processes attempt to perform `rename a/foo b/bar' and `rename b/bar
     a/foo', respectively, the system may deadlock attempting to lock both di-
     rectories for modification.  Hard links to directories should be replaced
     by symbolic links by the system administrator.

RETURN VALUES

     A 0 value is returned if the operation succeeds, otherwise rename() re-
     turns -1 and the global variable errno indicates the reason for the fail-
     ure.

ERRORS

     Rename() will fail and neither of the argument files will be affected if:

     [ENAMETOOLONG]
                   A component of a pathname exceeded {NAME_MAX} characters,
                   or an entire path name exceeded {PATH_MAX} characters.

     [ENOENT]      A component of the from path does not exist, or a path pre-
                   fix of to does not exist.

     [EACCES]      A component of either path prefix denies search permission.

     [EACCES]      The requested link requires writing in a directory with a
                   mode that denies write permission.

     [EPERM]       The directory containing from is marked sticky, and neither
                   the containing directory nor from are owned by the effec-
                   tive user ID.

     [EPERM]       The to file exists, the directory containing to is marked
     [EXDEV]       The link named by to and the file named by from are on dif-
                   ferent logical devices (file systems).  Note that this er-
                   ror code will not be returned if the implementation permits
                   cross-device links.

     [ENOSPC]      The directory in which the entry for the new name is being
                   placed cannot be extended because there is no space left on
                   the file system containing the directory.

     [EDQUOT]      The directory in which the entry for the new name is being
                   placed cannot be extended because the user's quota of disk
                   blocks on the file system containing the directory has been
                   exhausted.

     [EIO]         An I/O error occurred while making or updating a directory
                   entry.

     [EROFS]       The requested link requires writing in a directory on a
                   read-only file system.

     [EFAULT]      Path points outside the process's allocated address space.

     [EINVAL]      From is a parent directory of to, or an attempt is made to
                   rename `.' or `..'.

     [ENOTEMPTY]   To is a directory and is not empty.

SEE ALSO

     open(2) symlink(7)

STANDARDS

     The rename() function conforms to IEEE Std1003.1-1988 (``POSIX'').

4.2 Berkeley Distribution        June 4, 1993                                2