CHMOD(2)                             BSD                              CHMOD(2)



NAME
     chmod - change mode of file

SYNOPSIS
     chmod(path, mode)
     char *path;
     int mode;

     fchmod(fd, mode)
     int fd, mode;

DESCRIPTION
     chmod changes the mode of the file named by path to mode.  fchmod does
     the same thing for the file referenced by descriptor fd.  Modes are
     constructed by the logical OR of the following values:

          ISUID   04000   set user ID on execution
          ISGID   02000   set group ID on execution
          IREAD   00400   read by owner
          IWRITE  00200   write by owner
          IEXEC   00100   execute (search on directory) by owner
                  00070   read, write, execute (search) by group
                  00007   read, write, execute (search) by others

     Some UNIX implementations define ISVTX (01000) as the "sticky bit".  On
     those systems, if an executable file is set up for sharing (this is the
     default) then sticky bit prevents the system from abandoning the swap-
     space image of the program-text portion of the file when its last user
     terminates.  Ability to set this bit on executable files is restricted to
     the super-user.  When the sticky bit is set on a directory, an
     unprivileged user may not delete or rename files of other users in that
     directory.  Domain/OS BSD does not define the sticky bit.

     Only the owner of a file (or the super-user) can change the mode.

     Changing the owner of a file turns off the set-user-ID and set-group-id
     bits unless the user is the super-user (on other implementations, this is
     also true when writing a file).  This makes the system somewhat more
     secure by protecting set-user-ID (set-group-ID) files from remaining
     set-user-ID (set-group-ID) if they are modified, at the expense of a
     degree of compatibility.

ERRORS
     chmod will fail and the file mode will be unchanged if any of the
     following are true:

     [ENOTDIR]        A component of the path prefix is not a directory.

     [ENAMETOOLONG]   A component of a pathname exceeded 255 characters, or an
                      entire path 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]          The named file resides on a read-only file system.

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

     [EIO]            An I/O error occurred while reading from or writing to
                      the file system.

     fchmod will fail if any of the following are true:

     [EBADF]          The descriptor is not valid.

     [EINVAL]         fd refers to a socket, not to a file.

     [EROFS]          The file resides on a read-only file system.

     [EIO]            An I/O error occurred while reading from or writing to
                      the file system.

SEE ALSO
     chmod(1), open(2), chown(2), stat(2)

DIAGNOSTICS
     A successful call returns 0.  A failed call returns -1 and sets errno to
     indicate the error.

NOTES
     Some implementations also define the following errors:

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

     [EPERM]          The effective user ID does not match the owner of the
                      file and the effective user ID is not the super-user.