(To me) strange behaviour calling subs

[InDenial]

Hi everyone,

I have this weird behaviour. (maybe it is weird because I am not seeing what I am doing wrong).

I use the Net::Telnet module and I am trying to do some error handling.

The script has the following parts:

1. Connect to the switch
2. Login to the switch
3. Excecute some commands

I declared the $host variable in the beginning. In my understanding this means that the variable (when set) is known to the whole script. right?

I itterate through all the hosts in the @hosts array to do the mentioned parts. What I find strange is that when I call a sub from within the foreach loop I need to provide the $host everytime.

Ok now something goes wrong. I am trying to telnet using the wrong password. As you can see in the login sub I call the Errors sub. I did not provide the $host but the Errors sub knows what $host is.

Another component and something else goed wrong. I am trying to open a telnet connection but the component does not respond. again I call the Errors sub without the $host. This time from within the foreach loop but it gives me an error that it does not know $host.

I do have warnings and strict in the script and it does not give me any other errors.

I might be overlooking something so I hope someone can tell me what I am overlooking.

my $host;
my @hosts = qw(127.0.0.1 10.0.0.1);

my $t = new Net::Telnet (Timeout => 10, 
                      Prompt => '/\\\\user>/', 
                      Input_log => 'inputlog', 
                      Dump_log => 'dumplog', 
                      cmd_remove_mode => 0, 
                      Errmode => 'return'); 

$t->input_log(\*STDOUT);

foreach $host(@hosts){
	print OUTPUT "----------------Start $host----------\n";
	print OUTPUT "$host : Start Telnet\n";
	$command = "connect";
        if ($t->open("$host")) {
		if (&login($host)){
			&dostuff($host);
		}
	}
	else {[b]&Errors('CONERROR01)[/b]};
		
	print OUTPUT "----------End $host-------\n";
}


########### subs ##########################

sub Errors {
	my $error = $_[0];
	if ($command eq "connect" || $command eq "login"){
		print OUTPUT "$host : $command : $Errorlist{$error}\n";
	}
	else {
		my $lastline = $t->lastline;
		print OUTPUT "$host : $lastline\n";
	}
}

sub login {
	$host = $_[0];
	$command = "login";
	my ($prematch, $match) = $t->waitfor(Match => '/login: $/',
		Errmode => 'return');
	if (!$match) {
		&Errors('LIERROR01');
		return 0;
	}
	print OUTPUT $host." : Login prompt\n";
	$t->print("user");
	($prematch, $match) = $t->waitfor(Match => '/password: $/', 
		Errmode => 'return');
	if (!$match) {
		&Errors('LIERROR02');
		return 0;
	}
	print OUTPUT $host." : password prompt\n";
	$t->print("password");
	($prematch, $match) = $t->waitfor(Match => '/\\\\user>/', 
		Errmode => 'return');
	if (!$match){
		[b]&Errors('LIERROR03');[/b]
		return 0;
	}
	print OUTPUT $host." : Switch prompt\n";
}

InDenial

 

[InDenial]

Hmm the line:

else {&Errors('CONERROR01)}; should be

else {&Errors('CONERROR01')};

When setting it to bold I must have accidentaly deleted the '.

InDenial

 

[tchatzi]

Is this the whole script cause you said you [red]use strict;[/red] and [red]use warnings[/red] but your $command variable is not defined as 'my' or 'our'.

Now you shouldn't use 'my $host' for the whole script, and also use the same name inside your subroutines cause it redifines it. And you might end up having problems.

whats the point then of $host = $_[0]; if the whole script can see the $host, why dont you use it straight into the sub. It is not "that" recomended, but then again perl will not tell you anything if you do so.


``The wise man doesn't give the right answers,
he poses the right questions.''
TIMTOWTDI

 

[InDenial]

Thanks for the reply..

The above is the part of my script that matters I think. The script never changes the value of $host as far as I can see. (my knowledge is still somewhat limited).

I used the $host = $_[0]; because somehow that was the only way to get the $host variable into the sub.

The $command variable is also declared as an array in the beginning of the script using:

my $command = "";
my @commands = ("dir","netstat");

as a result of the above I decided to provide teh subs with the needed information. The script that follows works... but ofcourse I would appreciate some feedback...

#!/bin/perl -w 

use strict;
use warnings; 

########### Load Modules ######################## 

use Net::Telnet (); 

############ Prepare Variables ################## 
my $host;
my @hosts = qw(10.10.0.1 127.0.0.1);
my %Errorlist = (
	"CMDERROR01" => "The command took longer than the timeout of 10 seconds (Try increasing the timeout)",
	"LIERROR01" => "The script never saw the login prompt",
	"LIERROR02" => "The script never saw the password prompt(Probably error in script)",
	"LIERROR03" => "Wrong Username or Password",
	"CONERROR01" => "Unable to reach the switch through telnet"
);
my $command = "";
my @commands = ("dir","netstat");	

########### Prepare OUTPUT Files ################ 

my $output = 'outputfile';

########### Open OUTPUT Files ################ 

open (OUTPUT, ">$output") || die "can not open $output\n"; 

########### Telnet ############# 

my $t = new Net::Telnet (Timeout => 10, 
                      Prompt => '/\\\\user>/', 
                      Input_log => 'inputlog', 
                      Dump_log => 'dumplog', 
                      cmd_remove_mode => 0, 
                      Errmode => 'return'); 

$t->input_log(\*STDOUT);

foreach $host(@hosts){
	$command = "connect";
	print OUTPUT "Start $host-------------------\n";
	print OUTPUT "$host : $command : Start Telnet\n";
	if ($t->open("$host")) {
		print "Connected to : $host\n";
		$command = "login";
		if (&login($host,$command)){
			print "Logged In to : $host\n";
			&dostuff($host);
		}
	}
	else { 
		&Errors($host,$command,'CONERROR01')};
	
	print OUTPUT "End $host--------------------\n";
}

########### Close Output files ############

close OUTPUT;

########### subs ##########################

sub Errors {
	my ($a,$b,$c) = @_;
	print OUTPUT "$a : $b : $Errorlist{$c} ($c)\n";
}


sub login {
	my ($a,$b) = @_;
	my ($prematch, $match) = $t->waitfor(Match => '/login: $/',
		Errmode => 'return');
	if (!$match) {
		&Errors($a,$b,'LIERROR01');
		return 0;
	}
	print OUTPUT "$a : $b : Login prompt\n";
	$t->print("user");
	($prematch, $match) = $t->waitfor(Match => '/password: $/', 
		Errmode => 'return');
	if (!$match) {
		&Errors($a,$b,'LIERROR02');
		return 0;
	}
	print OUTPUT "$a : $b : password prompt\n";
	$t->print("password");
	($prematch, $match) = $t->waitfor(Match => '/\\\\user>/', 
		Errmode => 'return');
	if (!$match){
		&Errors($a,$b,'LIERROR03');
		return 0;
	}
	print OUTPUT "$a : $b : Switch prompt\n";
}

sub dostuff {
	my $a = $_[0];
	foreach $command (@commands){
		if($t->cmd(String => $command, Errmode => 'return')){
			print OUTPUT "$a : $command : \n";
		}
		else {
			&Errors($a,$command,'CMDERROR01');
			return 0;
		}
	}
}

InDenial