Method Getopt.find_option()

Method find_option

string|bool find_option(array(string) argv, array(string)|string shortform, array(string)|string|void longform, array(string)|string|void envvars, string|bool|void def, int|void throw_errors)

Description

This is a generic function to parse command line options of the type -f, --foo or --foo=bar.

Parameter argv

The first argument should be the array of strings that was sent as the second argument to your main() function.

Parameter shortform

The second is a string with the short form of your option. The short form must be only one character long. It can also be an array of strings, in which case any of the options in the array will be accepted.

Parameter longform

This is an alternative and maybe more readable way to give the same option. If you give "foo" as longform your program will accept --foo as argument. This argument can also be an array of strings, in which case any of the options in the array will be accepted.

Parameter envvars

This argument specifies an environment variable that can be used to specify the same option, to make it easier to customize program usage. It can also be an array of strings, in which case any of the mentioned variables in the array may be used.

Parameter def

This argument has two functions: It specifies if the option takes an argument or not, and it informs find_option() what to return if the option is not present.

The value may be one of:

int(0..0)|zero	The option does not require a value.
int(1..1)|string	The option requires a value, and def will be returned if the option is not present. If the option is present, but does not have an argument find_option() will fail. Note that a set option will always return a string, so setting def to 1 can be used to detect whether the option is present or not.

Parameter throw_errors

If throw_errors has been specified find_option() will throw errors on failure. If it has been left out, or is 0 (zero), it will instead print an error message on Stdio.stderr and exit the program with result code 1 on failure.

Returns

Returns the value the option has been set to if any.

If the option is present, but has not been set to anything 1 will be returned.

Otherwise if any of the environment variables specified in envvars has been set, that value will be returned.

If all else fails, def will be returned.

Throws

If an option that requires an argument lacks an argument and throw_errors is set an error will be thrown.

Note

find_option() modifies argv. Parsed options will be removed from argv. Elements of argv that have been removed entirely will be replaced with zeroes.

This function reads options even if they are written after the first non-option on the line.

Index 0 (zero) of argv is not scanned for options, since it is reserved for the program name.

Only the first ocurrance of an option will be parsed. To parse multiple ocurrances, call find_option() multiple times.

See also

Getopt.get_args()