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

O wise monks,

I have run into an issue at work where I need to automate the following:

  • SSH to an element
  • Run "Microcom /tmp/dev/mux1"
  • send "AT+CSQ" to that program
  • Retrieve the output in a variable in my script

    • I've accomplished the first (SSH to element and run command) but when it comes to actually sending anything to the interface and retrieve the output, I just cant get it to work.

    Relevant part of the code:

    $ssh->exec("microcom /tmp/dev/mux1");
$ssh->send("AT+CSQ");
$ssh->waitfor('^\+CSQ', 3) or warn "No output!";
$myOutput = $ssh->match();
print "CSQ result: $myOutput";

    [download]

    I've tried with ssh->exec("AT+CSQ") as well with no success. It simply warns on "No output!"

    Anyone done something similar before and can provide me with a hint or two on how to overcome this obstacle?

    If only I could pass the AT command directly on the commandline, but alas, thats not possible. :-(

    Thanks in advance!

    Replies are listed 'Best First'.
    Re: Net:SSH::Expect and microcom?
    by salva (Canon) on Nov 08, 2011 at 08:37 UTC
      Using Net::OpenSSH and Expect: 
      # untested
use Net::OpenSSH;

my $ssh = Net::OpenSSH->new(...);
my ($pty, $pid) = $ssh->open2pty('microcom /tmp/dev/mux1');

my $exp = Expect->init($pty);
$exp->send("AT+CSQ\r\n");
$exp->expect($timeout,
             [qr/^OK$/ => sub { ... }],
             [qr/^ERROR$/ => sub { ... }]);
$exp->soft_close();
waitpid($pid, 0);

      [download]
    		[reply]
    [d/l]

        Thanks, but it doesnt work. I am experiencing some very odd behaviour with the suggested snipped.

        When run manually, the AT command returns to OK within 500ms. Since the RegEx would match and it still times out, I believe it safe to conclude that it still doesnt pass in the AT command.

        More important is the fact that no matter what timeout I set, it throws the warning after ~2 seconds. I've set 50 seconds in the example below:

        print "Before timeout: " . localtime() . "\n";
my $timeout = 50;
$exp->expect($timeout,
    [qr/^OK$/ => sub { print "Success!\n"; }],
    [qr/^ERROR$/ => sub { print "Failure!\n"; }]) or warn "Timeout!";
print "After timeout: " . localtime() . "\n";

        [download]
        and the output I get from the above: 
        Before timeout: Tue Nov  8 03:31:02 2011
Timeout! at getdbm.pl line 18.
After timeout: Tue Nov  8 03:31:04 2011

        [download]

        Am I experiencing a bug here, or am I (still) an idiot?

    		[reply]
    [d/l]
    [select]
          Maybe you have to wait for microcom to settle before sending anything. Try sleeping for 1 second before sending the modem command.
    		[reply]
    Re: Net:SSH::Expect and microcom?
    by williams554 (Sexton) on Nov 07, 2011 at 22:33 UTC

      Hello,

      You need to tell it newline or return.

      $ssh->send("AT+CSQ\n"); or
      $ssh->send("AT+CSQ\r");
      Also, you can log what's going on
      string log_file
      Used as argument to the internal Expect->log_file() method.
      The default is no logfile.

      Good luck, Rob

    		[reply]
    Re: Net:SSH::Expect and microcom?
    by Anonymous Monk on Nov 07, 2011 at 22:15 UTC

      I've gotten a bit closer, but not quite there yet

      #!/usr/bin/perl

use strict;
use Net::SSH2;

my $ssh = Net::SSH2->new();

$ssh->connect('10.10.10.10') or die;

if ($ssh->auth_password('zzz','xxx')) {
  $ssh->debug(1);
  my $chan = $ssh->channel();
  $chan->shell();
  print $chan "microcom /tmp/dev/mux1\n";
  sleep(10);
  print $chan "AT+CSQ";
  select(undef,undef,undef,3.0);
  my ($len, $buf);
  print $buf while ($len = $chan->read($buf,1)) > 0;
  $chan->close;
} else {
  warn "auth failed.\n";
}

      [download]

      This one clearly shows me that the AT+CSQ is not passed on - when connecting to the modem, it will report "ERROR" after ~20 seconds of nothing going on. And it does just that. Any ideas on how to move on from here?

    		[reply]
    [d/l]

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