Use of uninitialized value $login_output in concatenation (.) or string at - perl

Question

in a .pl I have the following error (capture), the script is used through SPECTRUM, a network monitoring tool, and the script is used to capture the running config of a device, what could be the fault ? Thank you.
#!/opt/SPECTRUM/bin/perl -w
# This script will capture the running configuration of a
# Cisco SAN-OS device through an SSH session and print it to STDOUT.
#
# Error Codes:
# 0 = Success
# 255 = Usage error
# 254 = Invalid timeout value
# 252 = Login error
# 249 = Exec prompt not found error
# 244 = Error retrieving configuration
# 245 = Insufficient privileges
# 253 = Unexpected output
#
use strict;
use warnings;
use Net::SSH::Expect;
$ENV{'PATH'} = "/usr/bin:". $ENV{'PATH'};
### Main ###
if( $#ARGV != 4 && $#ARGV != 5 )
{
print "Usage: capture_running.pl <device IP> <user> <pass> <enable_pass>
<login_timeout_in_seconds> <capture_timeout_in_seconds>\n";
print STDERR "Usage: capture_running.pl <deviceIP> <user> <pass>
<enable_pass> <login_timeout_in_seconds> <capture_timeout_in_seconds>\n";
exit 255;
}
elsif( $ARGV[4] < 1 || $ARGV[4] > 600 )
{
print "$ARGV[4] is the login timeout and must be an int between 1 and 600 seconds\n";
print STDERR "$ARGV[4] is the login timeout and must be an int between 1 and 600 seconds\n";
exit 254;
}
elsif( $#ARGV == 5 && ( $ARGV[5] < 1 || $ARGV[5] > 600 ) )
{
print "$ARGV[5] is the capture timeout and must be an int between 1 and 600 seconds\n";
print STDERR "$ARGV[5] is the capture timeout and must be an int between 1 and 600 seconds\n";
exit 254;
}
else
{
my $capture_timeout = $ARGV[4];
if( $ARGV[5] )
{
$capture_timeout = $ARGV[5];
}
my $errorCode = 1;
my #data;
my $errorString = "\nHost $ARGV[0]: \n";
($errorCode, #data) = GetConfig( $ARGV[0], $ARGV[1], $ARGV[2], $ARGV[3],
$ARGV[4], $capture_timeout );
if( $errorCode == 0 )
{
# Success. The running configuration
# content is in the data variable
foreach ( #data ) { print "$_\n" }; # print the configuration to STDOUT
exit 0;
}
else
{
print STDERR $errorString;
if( $errorCode == 245 )
{
print STDERR join " ", #data, "\nEnsure that the device user has
sufficient privileges to disable paging and view the config\n";
}
else
{
print STDERR join " ", #data, "\n";
}
exit $errorCode;
}
}
exit 0;
sub GetConfig
{
my $deviceIP=shift;
my $user=shift;
my $pass=shift;
my $epass=shift;
my $login_timeout=shift;
my $capture_timeout=shift;
my #config;
my $msg;
my $ssh = Net::SSH::Expect->new ( host => $deviceIP,
user => $user,
password=> $pass,
raw_pty => 1,
no_terminal => 0,
timeout => $login_timeout,
ssh_option => '-1 -c DES'
);
my $login_output;
eval { $login_output = $ssh->login(); };
if( $# )
{
$msg = "Login has failed. Output: $login_output";
return( 252, $msg );
}
# login output should contain the right prompt characters
if( $login_output !~ /\>\s*\z/ )
{
$msg = "Login has failed. Didn't see device prompt as expected.";
$ssh->close();
return( 252, $msg );
}
if( $login_output !~ /\>\s*\z/ ) # Replace '#' is the prompt character here
{
# we don't have the '#' prompt, means we still can't exec commands
$msg = "Exec prompt not found.";
$ssh->close();
return( 249, $msg );
}
my $elogin = $ssh->exec("en");
my $elogin2 = $ssh->exec($epass);
if( $elogin2 !~ /\#\s*\z/ ) # Replace '#' is the prompt character here
{
$msg = "Exec prompt not found.";
$ssh->close();
return( 249, $msg );
}
# disable paging
# different commands for different devices, if they don't
# work then we will get messages about problems later
# specifically the "No prompt after 'sh run'" error
# errmsg doesn't get set when these error and if we use print
# and getlines to read for errors it causes problems with print "sh run"
# later.
# $ssh->exec( "term pager 0" );
my $paging = $ssh->exec( "term pager 0" );
if ( $paging =~ /\s?%\s/ )
{
$msg = "Unable to set terminal size to 0 - Insufficient privileges";
$ssh->close();
return( 245, $msg);
}
$ssh->send( "sh run" );
$ssh->timeout( $capture_timeout );
$ssh->peek(0);
while( my $line = $ssh->read_line() )
{
# get configuration content
if( $line !~
/sh run|Building configuration|Current configuration|^\s*$/ )
{
push #config, $line;
}
}
if( #config <= 0 )
{
$msg = "No data retrieved, the capture timeout may be too low.";
$ssh->close();
return( 244, $msg );
}
if( scalar grep { $_ =~ /^%/ } #config )
{
# Ensure show running actually returned the config and not an error
# message containing '%'
return( 245, #config );
}
return( 0, #config ); # everything was okay, return the captured data
}

Answer 1

It would really help us if you took the time to ensure the code you give us is well-formatted and as easy to read as possible.
But the code causing the problem is this:
my $login_output;
eval { $login_output = $ssh->login(); };
if( $# )
{
$msg = "Login has failed. Output: $login_output";
return( 252, $msg );
}
It's the only place where $login_output is used in a "concatenation (.) or string" as described in the error message.
So the the call to $ssh->login() is failing in such a way as to leave $login_output undefined.
I don't know anything about Net::SSH::Expect, but I suspect that you need to change the arguments to the new() call (a few lines above) in some way.
You'll get more information about what has gone wrong by adding $# to the debug output.

Answer 2

The most likely candidate for that error is this:
my $login_output;
eval { $login_output = $ssh->login(); };
if( $# )
{
$msg = "Login has failed. Output: $login_output"; # this line
return( 252, $msg );
}
Remove $login_output from that line since it will be uninitialized if login() dies/croaks. You can replace it with $# to get the message supplied to die/croak.