Net::SSH::Perl (Use of uninitialized value $stdout)

thanos1983 has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

My initial goal is to connect to a remote host though SSH apply one command or several (through bash script) catch the output and exit.

It seems and it is extremely easy but some unknown reason I can not get the output.

The message that I am getting is:

testOS: Use of uninitialized value $stdout in print at ssh.pl line 32.
[download]

With debug mode on (debug => 1), part of the output:

testOS: Use of uninitialized value $stdout in print at ssh.pl line 32.
testOS: channel 2: new [client-session]
testOS: Requesting channel_open for channel 2.
testOS: Entering interactive session.
testOS: Requesting service exec on channel 2.
testOS: channel 2: open confirm rwindow 0 rmax 32768
testOS: input_channel_request: rtype exit-status reply 0
testOS: channel 2: rcvd eof
testOS: channel 2: output open -> drain
testOS: channel 2: rcvd close
testOS: channel 2: input open -> closed
testOS: channel 2: close_read
testOS: channel 2: obuf empty
testOS: channel 2: output drain -> closed
testOS: channel 2: close_write
testOS: channel 2: send close
testOS: channel 2: full closed
[download]

Since this is my first Perl/ssh script, I am kind of lost. I run out of options, all the examples online point that it should be working.

Secondary question, in case that I want to execute a bash script through Perl/ssh is this syntax correct:

$cmd = `/bin/bash test.sh`;
[download]

And with script:

system("/bin/bash test.sh") == 0
    or die "Bash Script failed";
[download]

A working example:

#!/usr/bin/perl

use Expect;
use strict;
use warnings;
use Data::Dumper;
use Net::SSH::Perl; # SSH connection through Perl

$| = 1;

my $host = xxxx;
my $port = xxxx;
my $user = xxxx;
my $password = xxxx;
my $cmd = `ls -l`;
# my $cmd = `/bin/bash test.sh`;
#system("/bin/bash test.sh") == 0
#    or die "Bash Script failed";

my $ssh = Net::SSH::Perl->new( "".$host."" , 
                   port => "".$port."" ,
                   protocol => 2 ,
                   interactive => 1 ,
                   batchMode => 1 ,
                   RhostsAuthentication => 1,
                   debug => 1 );

$ssh->login("".$user."","".$password."");

my($stdout, $stderr, $exit) = $ssh->cmd($cmd);

#$ssh->shell;

print $stdout;
$ssh->cmd("exit");
[download]

If I remove the bash (#) from the $ssh->shell, I can even enter the remote terminal. But I just want to apply a script and exit remotely.

Thanks in advance for the time and effort.

Comment on Net::SSH::Perl (Use of uninitialized value $stdout) Select or Download Code

Replies are listed 'Best First'.
Re: Net::SSH::Perl (Use of uninitialized value $stdout) by boftx (Deacon) on May 21, 2014 at 14:31 UTC
Unless I am not fully awake yet, it appears that you are using backtics "`" as opposed to single quotes "'" to assign a value: my $cmd = `ls -l`; [download] The end effect of this is that you are telling perl to execute the command inside the backtics, and place any output from `STDOUT` in the variable `$cmd`. I presume that what you want is to assign the string consisting of 'ls -l' to `$cmd` which is then executed on the remote host. EDIT: Simplistic demo of above: $ cat backtictest.pl #!/usr/bin/perl use strict; use warnings; my $cmd_sq = 'ls -l'; print "Using single quotes: $cmd_sq\n\n"; my $cmd_bt = `ls -l`; print "Using backtics: $cmd_bt\n"; exit; __END__ Output: Macintosh-45:stuff user$ ./backtictest.pl Using single quotes: ls -l Using backtics: -rw-r--r-- 1 user group 260 May 6 17:58 Class1.pm -rw-r--r-- 1 user group 260 May 6 17:58 Class2.pm -rw-r--r-- 1 user group 331 May 6 17:58 MyExceptions.pm -rwx------ 1 user group 182 May 21 07:38 backtictest.pl [download] It helps to remember that the primary goal is to drain the swamp even when you are hip-deep in alligators.	[reply] [d/l] [select]
Re^2: Net::SSH::Perl (Use of uninitialized value $stdout) by thanos1983 (Parson) on May 21, 2014 at 14:55 UTC
To: boftx OMG, it was simple and I am spending so much time for something so simple. I guess when my brain get's stack to something keeps thinking that is correct. Thanks a lot for something so small I could end up spending the rest of the day just trying to figure out what was wrong.	[reply]