getopts smart positional-parameter parsingsuggest change
- getopts optstring name [args]
Parameter | Detail |
|———–|––––| | optstring | The option characters to be recognized | | name | Then name where parsed option is stored|
optstring : 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 (?) can 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 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
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,
name and, if not silent, prints an error message and unsets
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
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.