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GetOpt ignore required arguments

by stevensw (Acolyte)
on Aug 21, 2011 at 19:32 UTC ( #921546=perlquestion: print w/replies, xml ) Need Help??
stevensw has asked for the wisdom of the Perl Monks concerning the following question:

That is, arguments that are not option arguments, arguments that must always exist with or without options. In my case, just one argument is required and it is always at the very end. How to get getopt to ignore this field so it doesn't keep being treated like an option argument? Thanks

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Re: GetOpt ignore required arguments
by linuxer (Curate) on Aug 21, 2011 at 19:43 UTC

    So you are referring to Getopt::Std?

    Did you try to use -- to mark the end of the options? For example:

    ./ -opt1 -opt2 foo -- -take -us -as -arguments

    See the module documentation of Getopt::Std, which says:

    To allow programs to process arguments that look like switches, but aren't, both functions will stop processing switches when they see the argument --. The -- will be removed from @ARGV.
    • s/mark an end/mark the end/
    • added some missing paragraph tags
Re: GetOpt ignore required arguments
by Marshall (Abbot) on Aug 22, 2011 at 04:33 UTC
    It would really help if you showed some code and a specific situation.

    "How to get getopt to ignore this field?"
    Getopt already ignores what it does not understand. In the option string, you specify that an option takes an argument by the ':',semi-colon character. Getopt takes all of the stuff that it understands out of @ARGV and you process what it left over! In your case, sounds like exactly ONE thing should be left in @ARGV (see below). If you don't specify that an option needs an argument, then Getopt will leave the token after the option alone!

    I show some examples that sound like they are close to your situation below. Having an "standalone" argument that looks like an option (-abc or whatever) is a very unusual situation. One way of dealing with this has been posted and there are others. Before rolling further down that rabbit hole, show us an actual example of your problem.

    #!/usr/bin/perl -w use strict; use Getopt::Std; my %opts; my $usage = "usage: options [-a arga] [-b] mandatory_arg"; die "$usage \n" if !getopts("a:b", \%opts); die "error: arguments=".@ARGV." @ARGV\n$usage \n" if @ARGV !=1; print "ok\n"; __END__ # Wrong, "mandatory" used as -a's argument! C:\TEMP> -a mandatory error: arguments=0 usage: options [-a arga] [-b] mandatory_arg # Now ok! C:\TEMP>option -a arga mandatory ok # Error: b doesn't take an arg # looks like another mandatory arg! C:\TEMP>option -a -b arga mandatory error: arguments=2 arga mandatory usage: options [-a arga] [-b] mandatory_arg # -b doesn't expect an arg and that causes # error C:\TEMP> -b extra -a arga mandatory error: arguments=4 extra -a arga mandatory usage: options [-a arga] [-b] mandatory_arg # Now ok! C:\TEMP> -b -a arga mandatory ok
      OK I should have clarified that some of my options have optional arguments, that is 0 or 1 or more. This presented a problem when you do something like this: cmd -option mandatory_arg When -option is allowed any number of arguments, including 0. However I think I fixed my problem using a variation of what linuxer told me, basically set the last argument in the ARGV array to "--" before GetOptions is called.
        Yes, the idea that an option like "-a" sometimes has an arg and sometimes not, does present problems...
        [ -a [optional_arg ] ] Here -a is optional and its arg is optional (if there is a -a option).

        I personally would try to organize the UI so that each -option either has >= 1 args or no args. But I'm happy that you have a solution that works for your case! Thanks for reporting back on what worked for you!

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