$ chmod --help
Usage: chmod [OPTION]... MODE[,MODE]... FILE...
or: chmod [OPTION]... OCTAL-MODE FILE...
or: chmod [OPTION]... --reference=RFILE FILE...
Change the mode of each FILE to MODE.
With --reference, change the mode of each FILE to that of RFILE.
-c, --changes like verbose but report only when a change is made
-f, --silent, --quiet suppress most error messages
-v, --verbose output a diagnostic for every file processed
--no-preserve-root do not treat '/' specially (the default)
--preserve-root fail to operate recursively on '/'
--reference=RFILE use RFILE's mode instead of MODE values
-R, --recursive change files and directories recursively
--help display this help and exit
--version output version information and exit
Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: <http://www.gnu.org/software/coreutils/chmod>
or available locally via: info '(coreutils) chmod invocation'