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

Hi Monks,
I have a question regarding the Net::SSH2 module in ActiveState Perl for windows
I want to perform a for loop operation after connecting to a remote system. I have started a new shell from the channel module of Net::SSH2
In windows we need to provide the commands in the Channel's write method. But I do not know how to go ahead with writing a for loop using the write method.
Need some help pls.. Thx in advance..
J

Replies are listed 'Best First'.
Re: Net::SSH2 to execute for loop
by syphilis (Archbishop) on Jan 19, 2010 at 07:25 UTC
    Hi,

    This works for me on Win32, using Net::SSH2-0.18, built against an older version of libssh2, on perl-5.8: 
    use Net::SSH2;
use warnings;
use strict;

my $buflen = 10000;
my $buf1 = '0' x $buflen;

my $ssh2 = Net::SSH2->new();

$ssh2->connect('xxx.xxx.xxx.xxx') or die;

$ssh2->auth_password('xxx','xxxxxxx') or die "Unable to login $! \n";

my $chan = $ssh2->channel();

$chan->blocking(0);

$chan->shell();

for(1 .. 2) {

 if($_ == 1) {$chan->write("echo \$PATH\n")}
 else {$chan->write("echo \$HOME\n")}
 select(undef,undef,undef,0.25);

 $chan->read($buf1, $buflen);
 print "BUF1: ", $buf1, "\n";
}

$chan->close;

    [download]
    However, running Net::SSH2-0.28, built against the latest libssh2-1.2.2, the buffer is *empty* in the first iteration - but filled correctly in subsequent iterations of the loop.

    That is, with the older version of Net::SSH2 I'm getting: 
    BUF1: /usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/usr/games:/home/rob
+/bin

BUF1: /home/rob

    [download]
    but with the latest, I'm getting: 
    BUF1:

BUF1: /home/rob

    [download]
    I can hack my way around the problem with the latest Net::SSH2 by changing the loop to: 
    for($i = 0, $i < 2, $i++) {

 if($_ == 1) {$chan->write("echo \$PATH\n")}
 else {$chan->write("echo \$HOME\n")}
 select(undef,undef,undef,0.25);

 $chan->read($buf1, $buflen);
 if($buf1) {print "BUF1: ", $buf1, "\n"}
 else {
   print "Empty buffer ... trying again\n";
   --$i;
 }  
}

    [download]
    That then produces (running the latest Net::SSH2): 
    Empty buffer ... trying again
BUF1: /usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/usr/games:/home/rob
+/bin

BUF1: /home/rob

    [download]
    Hope there's something there that helps. (I don't have time to "tune" this script at the moment - or to look at the issue with the latest version.)

    Cheers,
    Rob
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