Question

I already did some research on Perl script debugging but couldn’t find what I was looking for.

Let me explain my problem here.

I have a Perl script which is not entering into last while loop it seems cos it is not printing anything inside as instructed.

So, I want to know is there any easier method available to see all lines one by one like we can see in shell script using

set -x

Here is my Perl script code

#!/usr/bin/perl -w

my $ZONEADM = "/usr/sbin/zoneadm list -c";

use strict;
use diagnostics;
use warnings;

system("clear");
print "Enter the app\n";
chomp(my $INS = <>);

print "\nEnter the Symmitrix ID\n";
chomp(my $SYMM = <>);

print "\nEnter the Server\n";
chomp(my $SRV = <>);

print "\nEnter the devices\n";
while (<>) {
  if($_ !~ m/(q|quit)/) {    
    chomp($_);
    my $TEMP_FILE = "/export/home/ptiwari/scripts/LOG.11";
    open (my $FH, '>>', $TEMP_FILE);
    my @arr = split(/:/, $_);
    if($arr[3]) {
      print $FH "/".$INS."db/".$arr[0]."  ".$SYMM."  ".$arr[1]."  ".$arr[2]."  ".$arr[3]."\n";
    }
    else {
      print $FH "/".$INS."db/".$arr[0]."  ".$SYMM."  ".$arr[1]."  ".$arr[2]."\n";
    }
    undef @arr;
    close $FH;
  }
  else {
    exit;
  }
}

my $IS_ZONE = qx($ZONEADM|grep -i $SRV|grep -v global);
if($IS_ZONE) {
  $IS_ZONE = "yes";
}
else {
  $IS_ZONE = "no";    
}    

open(my $FLH, '<', "/export/home/ptiwari/scripts/LOG.11");
my @lines;
while(<$FLH>) {
  my ($GLOBAL_MTPT, $SYM, $SYM_DEV, $SIZE, $NEWFS) = split;
  print $GLOBAL_MTPT."  ".$SYM."  ".$SYM_DEV;
  print "\n";
}

I already tried perl -d but it didn’t show me anything which can help me to troubleshoot why it didn’t enter the while loop.

Answer 1

Your while(<>) loop doesn’t have sensible termination conditions. The /q|quit/ regex is buggy.

1. You exit the whole script if any line contains q or quit. You will also exit, if the device descriptions contains things like quill or acquisition. The effect of typing an accidental q is similar to a CtrlC.

2. The only way to finish the loop and go on with the script is to send an EOF. This requires the user to punch CtrlD into the keyboard, or a file to simply end. Then your script will continue.

There are some other things wrong/weird with this script.
Main criticism: (a) all-uppercase variables are informally reserved for Perl and pragmatic modules. Lowercase or mixed case variables work too. (b) Your script contains quite some redundant code. Either refactor it into subs, or rewrite your logic

Here is an example rewrite that may be easier to debug / may not contain some of the bugs.

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

use constant DEBUG_FLAG => 1;  # set to false value for release
my $zoneadm_command = "/usr/sbin/zoneadm list -c";
my $temp_file_name = "/export/home/ptiwari/scripts/LOG.11";

sub prompt { print "\n", $_[0], "\n"; my $answer = <>; chomp $answer; return $answer }
sub DEBUG  { print STDERR "DEBUG> ", @_, "\n" if DEBUG_FLAG }

system("clear");
my $app_name = prompt("Enter the app");
my $symm_id  = prompt("Enter the Symmitrix ID");
my $server   = prompt("Enter the server name");
print "Enter the devices.\n";
print qq(\tTo terminate the script, type "q" or "quit".\n);
print qq(\tTo finish the list of devices, type Ctrl+D.\n);

open my $temp_file, ">>", $temp_file_name
    or die "Can't open log file: $!";

while (<>) {
  chomp; # remove trailing newline
  exit if /^q(?:uit)?$/; # terminate the script if the input line *is* `q` or `quit`. 
  my @field = split /:/;
  # grep: select all true values
  @field = grep {$_} ("/${app_name}db/$field[0]", $symm_id, @field[1 .. 3]);
  print $temp_file join("  ", @field), "\n";
}
close $temp_file;

DEBUG("finished the reading loop");

# get the zones with only *one* extra process
my @zones = 
    grep {not /global/}
    grep {/\Q$server\E/i}
    map  {chomp; $_}
        qx($zoneadm_command);
my $is_zone = @zones ? "yes" : "no";

DEBUG("Am I in the zone? $is_zone");

open my $device_file, "<", $temp_file_name or die "Can't open $temp_file_name: $!";

while (<$device_file>) {
  chomp;
  my ($global_mtpt, $sym, $sym_dev) = split;
  print join("  ", $global_mtpt, $sym, $sym_dev), "\n";
  # or short: print join("  ", (split)[0 .. 2]), "\n";
}