chmod(2)                                                 chmod(2)



     NAME
          chmod - change mode of file

     SYNOPSIS
          #include <sys/types.h>
          #include <sys/stat.h> int chmod(path, mode)
          char *path;
          mode_t mode;

     DESCRIPTION
          chmod sets the access permission portion of the named file's
          mode according to the bit pattern contained in mode.  The
          path points to a pathname naming a file.

          Access permission bits are interpreted as follows:

               04000  Set effective user ID on execution.

               02000  Set effective group ID on execution.

               01000  Save text image after execution.

               00400  Read by owner.

               00200  Write by owner.

               00100  Execute (search if a directory) by owner.

               00070  Read, write, execute (search) by group.

               00007  Read, write, execute (search) by others.

          The effective user ID of the calling process must match the
          owner of the file or be the superuser to change the mode of
          a file.

          If the effective user ID of the process is not the su-
          peruser, mode bit 01000 (save text image after execution) is
          cleared.

          If the effective user ID of the process is not the superuser
          and the effective group ID of the process does not match the
          group ID of the file, mode bit 02000 (set the effective
          group ID on execution) is cleared.

          If an executable file is prepared for sharing (see the cc -n
          option), then mode bit 01000 prevents the system from aban-
          doning the swap-space image of the program-text portion of
          the file when its last user terminates.  Thus, when the next
          user of the file executes it, the text need not be read from
          the file system but can simply be swapped in, saving time.




     April, 1990                                                     1

     chmod(2)                                                 chmod(2)



          Changing the owner of a file turns off the mode bit 04000
          (set user ID), unless the superuser does it.  This makes the
          system somewhat more secure at the expense of a degree of
          compatibility.

     RETURN VALUE
          On successful completion, a value of 0 is returned.  Other-
          wise, a value of -1 is returned and errno is set to indicate
          the error.

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

          [ENOTDIR]     A component of the path prefix is not a direc-
                        tory.

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

          [ELOOP]       Too many symbolic links were encountered in
                        translating a pathname.

          [ENOENT]      The named file does not exist.

          [EACCES]      Search permission is denied on a component of
                        the path prefix.

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

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

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

     SEE ALSO
          chmod(1), chown(2), open(2), stat(2), mknod(2), umask(2).













     2                                                     April, 1990