CHMOD(2)                   Linux Programmer's Manual                  CHMOD(2)

       chmod, fchmod - change permissions of a file

       #include <sys/types.h>
       #include <sys/stat.h>

       int chmod(const char *path, mode_t mode);
       int fchmod(int fildes, mode_t mode);

       The  mode of the file given by path or referenced by fildes is changed.

       Modes are specified by or'ing the following:

              S_ISUID   04000 set user ID on execution

              S_ISGID   02000 set group ID on execution

              S_ISVTX   01000 sticky bit

              S_IRUSR (S_IREAD)
                        00400 read by owner

              S_IWUSR (S_IWRITE)
                        00200 write by owner

              S_IXUSR (S_IEXEC)
                        00100 execute/search by owner

              S_IRGRP   00040 read by group

              S_IWGRP   00020 write by group

              S_IXGRP   00010 execute/search by group

              S_IROTH   00004 read by others

              S_IWOTH   00002 write by others

              S_IXOTH   00001 execute/search by others

       The effective UID of the process must be zero or must match  the  owner
       of the file.

       If  the  effective  UID of the process is not zero and the group of the
       file does not match the effective group ID of the process or one of its
       supplementary  group  IDs, the S_ISGID bit will be turned off, but this
       will not cause an error to be returned.

       Depending on the file system, set user ID and set  group  ID  execution
       bits  may  be  turned  off if a file is written.  On some file systems,
       only the super-user can set the sticky bit, which may  have  a  special
       meaning.  For the sticky bit, and for set user ID and set group ID bits
       on directories, see stat(2).

       On NFS file  systems,  restricting  the  permissions  will  immediately
       influence already open files, because the access control is done on the
       server, but open files are maintained by the client.  Widening the per-
       missions  may  be  delayed  for  other  clients if attribute caching is
       enabled on them.

       On success, zero is returned.  On error, -1 is returned, and  errno  is
       set appropriately.

       Depending  on  the file system, other errors can be returned.  The more
       general errors for chmod are listed below:

       EPERM  The effective UID does not match the owner of the file,  and  is
              not zero.

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

       EFAULT path points outside your accessible address space.

              path is too long.

       ENOENT The file does not exist.

       ENOMEM Insufficient kernel memory was available.

              A component of the path prefix is not a directory.

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

       ELOOP  Too many symbolic links were encountered in resolving path.

       EIO    An I/O error occurred.

       The general errors for fchmod are listed below:

       EBADF  The file descriptor fildes is not valid.

       EROFS  See above.

       EPERM  See above.

       EIO    See above.

       The  chmod  call  conforms  to SVr4, SVID, POSIX, X/OPEN, 4.4BSD.  SVr4
       documents EINTR, ENOLINK and EMULTIHOP returns, but no ENOMEM.  POSIX.1
       does not document EFAULT, ENOMEM, ELOOP or EIO error conditions, or the
       macros S_IREAD, S_IWRITE and S_IEXEC.

       The fchmod call conforms to 4.4BSD and SVr4.  SVr4 documents additional
       EINTR and ENOLINK error conditions.  POSIX requires the fchmod function
       is  defined,  and  documents  additional ENOSYS and EINVAL error condi-
       tions, but does not document EIO.

       POSIX and X/OPEN do not document the sticky bit.

       open(2), chown(2), execve(2), stat(2)

Linux 2.0.32                      1997-12-10                          CHMOD(2)