Here's my script to do it. It's called desc.
$ desc cp
cp [OPTION]... [-T] SOURCE DEST
cp [OPTION]... SOURCE... DIRECTORY
cp [OPTION]... -t DIRECTORY SOURCE...
$ desc gcc -dD
-dD Dump all macro definitions, at the end of preprocessing, in addition to normal output.
$ desc rsync -v
-v, --verbose increase verbosity
$ desc bash getopts
getopts optstring name [args]
getopts is used by shell procedures to parse positional parameters. optstring contains the option characters to be recognized; if a character is followed by a colon, the option is
expected to have an argument, which should be separated from it by white space. The colon and question mark characters may not be used as option characters. Each time it is invoked,
getopts places the next option in the shell variable name, initializing name if it does not exist, and the index of the next argument to be processed into the variable OPTIND. OPTIND is
initialized to 1 each time the shell or a shell script is invoked. When an option requires an argument, getopts places that argument into the variable OPTARG. The shell does not reset
OPTIND automatically; it must be manually reset between multiple calls to getopts within the same shell invocation if a new set of parameters is to be used.
When the end of options is encountered, getopts exits with a return value greater than zero. OPTIND is set to the index of the first non-option argument, and name is set to ?.
getopts normally parses the positional parameters, but if more arguments are given in args, getopts parses those instead.
getopts can report errors in two ways. If the first character of optstring is a colon, silent error reporting is used. In normal operation diagnostic messages are printed when invalid
options or missing option arguments are encountered. If the variable OPTERR is set to 0, no error messages will be displayed, even if the first character of optstring is not a colon.
If an invalid option is seen, getopts places ? into name and, if not silent, prints an error message and unsets OPTARG. If getopts is silent, the option character found is placed in
OPTARG and no diagnostic message is printed.
If a required argument is not found, and getopts is not silent, a question mark (?) is placed in name, OPTARG is unset, and a diagnostic message is printed. If getopts is silent, then a
colon (:) is placed in name and OPTARG is set to the option character found.
getopts returns true if an option, specified or unspecified, is found. It returns false if the end of options is encountered or an error occurs.
But if you don't have access to a script like that, just run
less, then type
/^ *-option (note the space), for example, in the
gcc man page, type
/^ *-dDEnter to find the documentation for the
This works because the option usually appears at the start of the line.