handling switches with no argument using GetOpt::Long

bahadur has asked for the wisdom of the Perl Monks concerning the following question:

Hi monks, this is my code

Getopt::Long::GetOptions
        (
        'u=s' => \$user,
        'p=s' => \$passwd,
        's=s' => sub { local *_ = \$_[1];
        /^([^:]+):(\d+)$/ or die("Invalid format for option s.\n");
        $host = $1;
        $port = $2;},
        )
        or error_detect("3 Invalid commmand line options.");
[download]

now this code handles the switches u, p and s. but suppose i am supposed to give a command line swtich like h which does nothing but to invoke a help message. how do that with it.
what i mean is that all switches require some sort of argument. but if the user types in the switch -h than no argument is required with it and the program should directly print a help message.
so how does GetOpt::Long handle switches which do not require any arguments with them and their mere presence means a specific action is to be done. other examples of such switches can be -all etc etc.

Comment on handling switches with no argument using GetOpt::Long Download Code

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Re: handling switches with no argument using GetOpt::Long by Joost (Canon) on May 19, 2005 at 11:28 UTC
Have you looked at the documentation? It's the first type of option in there ("Simple options"). `GetOptions( 'help' => \$help, );` [download] "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re: handling switches with no argument using GetOpt::Long by holli (Abbot) on May 19, 2005 at 11:27 UTC
did you read the docs? Handling simple options is straightforward: `my $verbose = ''; # option variable with default value (false) my $all = ''; # option variable with default value (false) GetOptions ('verbose' => \$verbose, 'all' => \$all);` [download] The call to GetOptions() parses the command line arguments that are present in @ARGV and sets the option variable to the value 1 if the option did occur on the command line. Otherwise, the option variable is not touched. Setting the option value to true is often called enabling the option. holli, /regexed monk/	[reply] [d/l]