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

Hi Monks,

First off, I'm not a competent Perl coder, so please forgive me if this is obvious....

I'm trying to get the following code to execute two commands on a remote machine using Net::OpenSSH. I can login and execute the first command ok, but the second command simply returns "Connection to x.x.x.x closed by remote host." By introducing a delay before the 2nd command and looking at netstat I can see that the connection is still open, right up until the second command is attempted. In fact netstat looks like: 

netstat -an | grep x.x.x.x
tcp        0      0 x.x.x.x:55942       x.x.x.x:22           ESTABLISH
+ED 
unix  2      [ ACC ]     STREAM     LISTENING     7356830 /home/cstron
+g/.libnet-openssh-perl/root-10.224.138.142-26229-724671

[download]
Is it even possible to execute two commands without opening two connections to the remote machine? Where am I going wrong?!

Thanks Monks! 
#!/usr/bin/perl

use Net::OpenSSH;

$ip="x.x.x.x";
$user="xx";
$pass="xx";

($ssh)=&connect_ssh($ip, $user, $pass);  

@arry = $ssh->capture("ps -ef");


while (@arry)
{
 $line=shift @arry;
 print "MATCH1 $line";
}


@arry = $ssh->capture("ps -ef");


while (@arry)
{
 $line=shift @arry;
 print "MATCH2 $line";
}


sub connect_ssh
{
 my $ip = shift;
 my $user = shift;
 my $pass = shift;
 my $ssh = Net::OpenSSH->new(   $ip,
 strict_mode => '0',
 user     =>     $user,
 password =>     $pass,
 timeout  =>     '60');
 return ($ssh);
}

[download]

By the way, I know running twp "ps -ef" is pointless, but I'm just trying to illustrate the fact that I can't get a second command to run.

I have openssl installed and normal ssh works perfectly fine.

openssl version OpenSSL 0.9.8g 19 Oct 2007

Replies are listed 'Best First'.
Re: Net::OpenSSH multiple commands
by salva (Canon) on Sep 18, 2009 at 14:53 UTC
    I can't see anything wrong in your script!

    Net::OpenSSH has a debug mode that will tell you what's going on. Just add the following line at the beginning of your script: 

    $Net::OpenSSH::debug = -1;

    [download]
    Also, can you tell us the versions of the software you are using, including the OS, perl, Net::OpenSSH, the local SSH client and the remote SSH server?
[reply]
[d/l]
      Thanks Salva for your response

      I'm running

      Fedora release 9 (Sulphur)

      Perl v5.10.0 built for i386-linux-thread-multi

      openssh-5.1p1

      Local SSH client is OpenSSH_5.1p1, OpenSSL 0.9.8g 19 Oct 2007

      Remote SSH server is OpenSSH_2.5.2p2, SSH protocols 1.5/2.0

      Debug output is as follows: 
      # call args: ['ssh','-S','/home/cstrong/.libnet-openssh-perl/root-10.2
+24.138.142-26522-522395','-o','User=root','--','10.224.138.142','ps -
+ef']
# open_ex: ['ssh','-S','/home/cstrong/.libnet-openssh-perl/root-10.224
+.138.142-26522-522395','-o','User=root','--','10.224.138.142','ps -ef
+']
Connection to 10.224.138.142 closed by remote host.
# set_error(5 - child exited with code 255)
# DESTROY(Net::OpenSSH=HASH(0x949885c), pid => 26523)
# call args: ['ssh','-O','exit','-S','/home/cstrong/.libnet-openssh-pe
+rl/root-10.224.138.142-26522-522395','-o','User=root','--','10.224.13
+8.142']
# open_ex: ['ssh','-O','exit','-S','/home/cstrong/.libnet-openssh-perl
+/root-10.224.138.142-26522-522395','-o','User=root','--','10.224.138.
+142']
# set_error(5 - child exited with code 255)

      [download]
[reply]
[d/l]
        Remote SSH server is OpenSSH_2.5.2p2, SSH protocols 1.5/2.0

        That's quite old (~2001) and probably the cause of your problems... the only workaround besides upgrading the server would be to open a new connection for every command.

        Anyway, you (or the corresponding party) should upgrade the server software even if only for security reasons!

[reply]
        Sorry, forgot to say that the debug ouput just posted is shown after the output of the first "ps -ef" - i.e. the important bit!
[reply]

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