Empty string checking in output

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

use Net::Cisco;
open(CONFIG,">config.csv");
print CONFIG "Router ip,Status\n";
open(ROUTERIP,"routerip.txt")or die "couldn't open routerip.txt";
open(COMMAND,"command.txt")or die "couldn't open command.txt";
while(<COMMAND>)
{
    chomp($_);
    $comm=$_;
}
$count=0;
while(<ROUTERIP>)
{
chomp($_);
$router=$_;
$tl=0;
tel($router);
$count++;
}
sub tel
{
$t =Net::Telnet::Cisco->new(Host=>$router,Timeout=>7,Errmode=>'return'
+) or $tl=1;
$lg=0;
my @output;
if($tl != 1)
{
print "$router Telnet success\n";
$t->login('vinth_vm', 'h0mes@ker') or $lg=1 ;
    if($lg != 1)
    {
    print "$router Login success\n";
    @output=$t->cmd(string=>"$comm");
        if(@output ne '')
        {
        chomp(@output);
        print "@output\n";
        print CONFIG "$router,@output\n";
        
        }
        else
        {
        print "no config\n";
        print CONFIG "$router,no config\n";
        }
    $t->close;
    }
    else
    {
    $loginstat="Login Failed";
    print "$router $loginstat\n";
    print CONFIG "$router,$loginstat\n";
    }
}
else
{
$telnetstat="Telnet Failed";
print "$router $telnetstat\n";
print CONFIG "$router,$telnetstat\n";
}
}
close(CONFIG);
[download]

my code is for telnet into cisco router and execute a command and if that configuration exist then write that to one file but there is no configuration then it should write in output file as "no config" here the problem is with

if(@output ne '')
        {
        chomp(@output);
        print "@output\n";
        print CONFIG "$router,@output\n";
        
        }
        else
        {
        print "no config\n";
        print CONFIG "$router,no config\n";
        }
[download]

part i dont know why ,if the configuration is there then in cisco it wont display any thing at that time ,i want to write as "no config" but its not happening ,the problem is with string comparison ,,,can any body help me?

Comment on Empty string checking in output Select or Download Code

Replies are listed 'Best First'.
Re: Empty string checking in output by toolic (Bishop) on Aug 16, 2011 at 12:53 UTC
if(@output ne '') That will always evaluate to true since an array evaluated in scalar context returns the number of elements (0, 1, 2, etc.); it will not return the empty string. Perhaps this will be better: `if(@output)` [download]	[reply] [d/l]
Re^2: Empty string checking in output by Kumar Mantri (Novice) on Aug 17, 2011 at 05:02 UTC
tulic , i tried that but the else block is not executing. i can explain the behavior of the cisco device if a particular command is not present... if i telnet into cisco device it will show as `2960#` [download] here at this prompt i want to check one command i.e `2960#sh run \| in ntp` [download] if the configuration is not present then it will show as same `2960#` [download] so at this time the in array @output doesn't contain anything but i dont know why the else block is not executing	[reply] [d/l] [select]
Re^3: Empty string checking in output by AnomalousMonk (Archbishop) on Aug 17, 2011 at 06:32 UTC
... the in array @output doesn't contain anything but ... the else block is not executing ... ... because, contrary to what you think, the `@output` array contains something. Try printing/dumping the contents of the array. Also, what code are you actually running? `>perl -wMstrict -le "my @output = (); ;; if (@output) { print qq{true clause: array not empty}; } else { print qq{false clause: array empty}; } " false clause: array empty` [download]	[reply] [d/l] [select]
Re^4: Empty string checking in output by Kumar Mantri (Novice) on Aug 17, 2011 at 09:12 UTC
Re^5: Empty string checking in output by AnomalousMonk (Archbishop) on Aug 17, 2011 at 13:56 UTC
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