chmod(1) - change file mode bits
The  format  of  a  symbolic  mode  is  [ugoa...][[+-=][perms...]...], where perms is either zero or more
letters from the set rwxXst, or a single letter from the set ugo.  Multiple symbolic modes can be  given,
separated by commas.
Change the mode of each FILE to MODE.
-c, --changes
       like verbose but report only when a change is made
       do not treat `/' specially (the default)
       fail to operate recursively on `/'
-f, --silent, --quiet
       suppress most error messages
-v, --verbose
       output a diagnostic for every file processed
       use RFILE's mode instead of MODE values
-R, --recursive
       change files and directories recursively
--help display this help and exit
       output version information and exit