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

Fellow monks, I am having a problem using $ARGV as I intend, here is the problem:

I am trying to force that 3 mandatory arguments are included at execution. for example: 

die "Usage: $0 [arg] [arg] [arg]\n" 
unless ($ARGV[0], $ARGV[1], $ARGV[2]);

[download]

However, this doesn't work... Any ideas what will?

Replies are listed 'Best First'.
Re: $ARGV dilemma
by blue_cowdawg (Monsignor) on May 27, 2001 at 15:42 UTC

    Check out the following: 

    --$  cat argvtest.pl 
#!/usr/bin/perl -w 
###################################################################
use strict;

print "too few$/" if scalar(@ARGV) < 3 ;
print "just right$/" if scalar(@ARGV) == 3;
print "too many$/" if scalar(@ARGV) > 3;
--$  perl argvtest.pl 1 2
too few
--$  perl argvtest.pl 1 2 3
just right
--$  perl argvtest.pl 1 2 3 4
too many
--$

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    scalar is your friend! ;-)
    HTH

    Peter L. BergholdSchooner Technology Consulting, Inc.
    Peter@Berghold.Netwww.berghold.net
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[d/l]
      Doesn't numeric comparison already put it in scalar context? i.e. isn't 
      print "too few$/" if scalar(@ARGV) < 3;

      [download]
      Equivalent to: 
      print "too few$/" if @ARGV < 3;

      [download]
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[d/l]
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        While I can't show you an example: I have seen numeric comparisons not work. Wish I could remember where it happened but it was a while ago...

        Peter L. BergholdSchooner Technology Consulting, Inc.
        Peter@Berghold.Netwww.berghold.net
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Re: $ARGV dilemma
by dusk (Friar) on May 27, 2001 at 06:11 UTC
    UPDATE: Err, I answered my own question right after submission; I apologize for asking such a silly question, and jumping to ask, before giving it any thought.
    The solution is, of course, to just use unless $ARGV[2].

    UPDATE 2: I guess I should have been more precise in both my question and update. Originally, the last argument was 0; but changing it to a string was the solution I came up with..

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[d/l]
        unless $ARGV[2] works until someone passes a zero. You could amend it to   unless defined $ARGV[2] though   if 3 > @ARGV reads better, at least in my opinion.

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[d/l]
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      That won't always work.

      What if @ARGV = ("0","0","0"). Then $ARGV[2] is false and you get an error despite having three arguments.

      You probably like something like unless @ARGV == 3.

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[d/l]
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