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Re: Testing <> for undefined

by danielcid (Scribe)
on Jul 08, 2004 at 15:59 UTC ( [id://372842]=note: print w/replies, xml ) Need Help??


in reply to Testing <> for undefined

*fixing my previous post:

You could also do something like that: 
# Test if the is an argument 

if(!@ARGV) 
   { 
   die "My help message\n"; 
   } 

# Test if the argument is a file 
if(! -e $ARGV[0]) 
   { 
   print "File $ARGV0 does not exist\n"; 
   }

[download]
's -DBC

Replies are listed 'Best First'.
Re^2: Testing <> for undefined
by BbTrumpet (Acolyte) on Jul 08, 2004 at 16:41 UTC
    I have done this in the past, and it seems to work fine: 
    my $file = $ARGV[0] ? $ARGV[0] : die "USAGE:  prog.pl file_pathname\n";
open(FILE,"$file") or die "Unable to open file $file\n";
[reply]
      I have to say that I hate your use of the trinary operator there. You're expressing that you want to assign die's result to $file. Instead: 
      my $file = $ARGV[0] or die "Usage: prog.pl file_pathname\n";

      [download]
      (as a bonus, you don't have the redundant mention of $ARGV[0]).
      Better, if the filename might be zero: 
      @ARGV or die "Usage: prog.pl file_pathname\n";
my $file = $ARGV[0];

      [download]
      We're not really tightening our belts, it just feels that way because we're getting fatter.
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