CHMOD(2)                                                              CHMOD(2)


NAME
       chmod - change mode of file

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

       fchmod(fd, mode)
       int fd, mode;

DESCRIPTION
       The file whose name is given by path or referenced by the descriptor fd
       has its mode changed to mode.  Modes are constructed by or’ing together
       some combination of the following, defined in <sys/inode.h>:

              ISUID   04000   set user ID on execution
              ISGID   02000   set group ID on execution
              ISVTX   01000   ‘sticky bit’ (see below)
              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

       If  an executable file is set up for sharing (this is the default) then
       mode ISVTX (the ‘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.

       If mode ISVTX (the ‘sticky bit’) is set on a directory, an unprivileged
       user may not delete or rename files of other users in  that  directory.
       For more details of the properties of the sticky bit, see sticky(8).

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

       Writing  or  changing the owner of a file turns off the set-user-id and
       set-group-id bits unless the user is the super-user.   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.

RETURN VALUE
       Upon  successful  completion,  a  value of 0 is returned.  Otherwise, 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:

       [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 characters, or an
                      entire path name 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.

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

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

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

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

       Fchmod will fail if:

       [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), sticky(8)


4th Berkeley Distribution        May 13, 1986                         CHMOD(2)
 
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