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

I'm trying to have default data in case a command line argument is missing.
There must be a better way of doing this... 
my $fileold = "ArchLDAP";
my $filenew = "LDAP";
my $infileold = $ARGV[0];
   if ($infileold eq "") {
      $infileold = $fileold;
      }
my $infilenew = $ARGV[1];
   if ($infilenew eq "") {
      $infilenew = $filenew;
      }

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Your humble servant
-Chuck

Replies are listed 'Best First'.
Re: Defaults for command line args
by btrott (Parson) on May 15, 2000 at 22:25 UTC
    How about: 
        my $infileold = $ARGV[0] || $fileold;
    my $infilenew = $ARGV[1] || $filenew;

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    Or, if you want to get rid of those args from @ARGV, you could use shift: 
        my $infileold = shift || $fileold;
    my $infilenew = shift || $filenew;

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RE: Defaults for command line args
by vroom (His Eminence) on May 15, 2000 at 22:26 UTC
    That's what ||= is for. 
    $infile ||= "blah";
#this will only set $infile="blah" when $infile is undefined.

    [download]
    Or there's always 
    $infile= ? $infile : "default";

    [download]


    vroom | Tim Vroom | vroom@cs.hope.edu
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RE: Defaults for command line args
by mikfire (Deacon) on May 15, 2000 at 22:26 UTC
    Try something like this: 
    my $fileold = "ArchLDAP";
my $filenew = "LDAP";
my $infileold = $ARGV[0] || $fileold;
my $infilenew = $ARGV[1] || $filenew;

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    Mik
    Mik Firestone ( perlus bigotus maximus )
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Re: Defaults for command line args
by lhoward (Vicar) on May 15, 2000 at 23:51 UTC
    For more complicated command-line argument parsing you may want to check out the Getopt::Long and Getopt::Std modules.
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Re: Defaults for command line args
by mdillon (Priest) on May 15, 2000 at 22:26 UTC
    this isn't really "better", but it looks nicer: 
    my $infileold = (@ARGV) ? shift @ARGV : "ArchLDAP";
my $infilenew = (@ARGV) ? shift @ARGV : "LDAP";

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      The problem with this is that @ARGV could be non-empty but its elements could be undef or empty strings. So your test for "if (@ARGV)" would pass, but the variable would get assigned an empty string. Consider what happens if the scripts is called like this: 
      ./prog.pl ""

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      In this case @ARGV is not empty, but its first element is an empty string.

      --ZZamboni

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        yeah, i thought of that, but i was over editing my answer when i saw three other answers which together covered every aspect of the problem. i think the best is btrott's solution: 
        my $infileold = shift || $fileold;

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