"Getoptions'" argument syntax

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

Greetings,

I was studying someone else's code and came across this line:

GetOptions(
"refresh=i" => \ (my $REFRESH = 10),
...other option variables...
  );
[download]

I'm confused by the syntax of this line. It is nowhere to be found in the module documentation. According to the module, the "=" sign in "refresh=i" makes the option mandatory in the command line. So if that's the case, why does the argument above appear to be assigning a value to "$REFRESH"?

Respectfully Yours,

$PM = "Perl Monk's";
$MCF = "Most Clueless ~~Friar~~ Abbot";
$nysus = $PM . $MCF;

Comment on "Getoptions'" argument syntax Download Code

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Re: "Getoptions'" argument syntax by wog (Curate) on Jun 15, 2001 at 23:36 UTC
That code is another way of saying: `my $REFRESH = 10; GetOptions( "refresh=i" => \$REFRESH, ...... );` [download] You can think of the my as both representing and declaring the lexical variable(s) in question. update: The reason it's a `=i` and not a `:i` is that the `=i` makes the number mandatory after the option, but not the option.	[reply] [d/l] [select]
Re: Re: "Getoptions'" argument syntax by nysus (Parson) on Jun 15, 2001 at 23:42 UTC
OK, thanks. But still, if $REFRESH is required to be given a value from command line, why bother setting it to 10? Why not make the command optional with a ":". This is merlyn's code so I'm assuming a guru like that would have some logic behind this but maybe I'm wrong. $PM = "Perl Monk's"; $MCF = "Most Clueless ~~Friar~~ Abbot"; $nysus = $PM . $MCF;	[reply]
Re: Re: Re: "Getoptions'" argument syntax by Anonymous Monk on Jun 16, 2001 at 00:29 UTC
'=' means that: If you give the option you must(mandatory) give an argument. To give the option although is optional. ':' means you can give the option with or without an argument.	[reply]
Re: "Getoptions'" argument syntax by btrott (Parson) on Jun 16, 2001 at 00:15 UTC
The '=' in 'refresh=i' doesn't mean that 'refresh' is a mandatory option to the program. It means that, if 'refresh' is supplied, the integer argument is mandatory. So you can't just have `$ foo.pl --refresh` [download] An argument to 'refresh' is mandatory. I don't think there is a way to indicate that an option is mandatory (ie. that 'refresh' must be provided as an option). And since 'refresh' may not be provided, the `$REFRESH = 10` [download] sets the default value for 'refresh' to 10. And it can be overriden on the command line with '--refresh'.	[reply] [d/l] [select]
Re: "Getoptions'" argument syntax by mikfire (Deacon) on Jun 16, 2001 at 00:08 UTC
`borris)cat getopt.pl #!usr/bin/perl -w use Getopt::Long; use strict; GetOptions( "refresh=i", \ (my $refresh = 10 ) ); print "refresh = $refresh\n"; borris)perl getopt.pl refresh = 10 borris)perl getopt.pl -refresh 5 refresh = 5` [download] Quick experimentation suggests that it provides a default value for an optional parameter. Which is really quite neat, and seems to be completely undocumented. mikfire	[reply] [d/l]
Re: Re: "Getoptions'" argument syntax by wog (Curate) on Jun 16, 2001 at 00:15 UTC
... seems to be completely undocumented. Getopt::Long's documentation does document it, though not directly (emphasis added): 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. It's just a little leap from that that you can take advantage of having an option's variable set before its passed to `GetOptions`, which is what the odd code given does.	[reply] [d/l]


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