Question

How would I solve the following error:

readline() on unopened filehandle UPPER at faStat2 line 86.

in the following code?

#!/usr/bin/perl
use strict;
use warnings;

...

my $cmd = $0;
$cmd =~ s#.*/##;

($#ARGV > 0) || die "Usage $cmd <tibcoUpperMDLog> <tibcoLowerMDLog> <outFile>\n\n";

open(my $UPPER, $ARGV[0]) || die "Unable to open $ARGV[0]\n";
open(my $LOWER, $ARGV[1]) || die "Unable to open $ARGV[1]\n";

...

while ($msg = <UPPER>) { getUpperBusTimeStampAndBatchSize(\$msg); } #This is the line that the error is complaning about

Answer 1

Here I include both practical and stylistic chages.

#!/usr/bin/perl
use strict;
use warnings;

...

my $cmd = $0;
$cmd =~ s#.*/##;

die "Usage $cmd <tibcoUpperMDLog> <tibcoLowerMDLog> <outFile>\n\n"
  unless @ARGV > 2;

open my $upper, '<', $ARGV[0] or die "Unable to open $ARGV[0]\n";
open my $lower, '<', $ARGV[1] or die "Unable to open $ARGV[1]\n";

...

while ($msg = <$upper>) { getUpperBusTimeStampAndBatchSize(\$msg); }

Practical:

• 3 arg open (safer, modern)
• fixed consistent use of indirect filehandles

Stylistic:

• using or rather than braces and || (least important)
• compare against @ARGV rather than $#ARGV (more readable, “need at least 2 args”)
• use lower case on lexical (my) variables