How to open the channel and push the data into while loop? - perl

Question

I am trying to traverse the ls | grep command in to the channel, which is while looping and pushing the output to the #output array. But, while loop is not providing the necessary output because of which the code will die with die "could not find the file $_[1] in $Source to $Destination \n" unless(#output);. If I comment the die part of the code and proceed with the copy from source to destination is not working.
Here is part of my code:
my $host ="$hash{Linux_Server_IP}";
my $Uname = "$hash{Linux_Server_Username}";
my $password ="$hash{Linux_Server_Password}";
my $ssh2= Net::SSH2->new();
$ssh2->connect($host)or die "Could not connect : $# \n ";
$ssh2->auth_password($Uname,$password) or die "Could not login : Reason : $#\n";
$ssh2->blocking();
our $chnl = $ssh2->channel();
$chnl->shell();
print $chnl "ls | grep $_[1] \n";
my #output;
sleep(1);
while (<$chnl>){push #output,$_};
die "could not find the file $_[1] in $Source to $Destination \n" unless(#output);
print $chnl "cp $Source $Destination \n";
Error in the log:
could not find the file ABC.csv in /data/Directory1/ABC.csv to /data/Directory2/ABC.csv
I manually verified the file on the server and it does exist. Please advise.

Answer 1

Quoting Net::SSH2::Channel
Alternatively, it is also possible to launch a remote shell (using
shell) and simulate the user interaction printing commands to its
stdin stream and reading data back from its stdout and stderr. But
this approach should be avoided if possible; talking to a shell is
difficult and, in general, unreliable.
Furthermore using ls to detect if a file/directory exists is fragile and unreliable. You should use file test operations instead, e.g.
sub exec_remote($$) {
my($ssh2, $cmd) = #_;
# every exec() requires a new channel
my $chan = $ssh2->channel()
or $ssh2->die_with_error;
# send command to remote
$chan->exec($cmd)
or $ssh2->die_with_error;
# we're done from our side
$chan->send_eof;
# ignore command output
while (<$chan>) {}
# wait for remote command to complete and return its exit status
return $chan->exit_status;
}
sub copy_remote_if_necessary($$$$) {
my($ssh2, $source, $destination, $file) = #_;
if (exec_remote($ssh2, "/usr/bin/test -f ${destination}/${file}") ne 0) {
die "Copy failed!\n"
unless (exec_remote($ssh2, "cp ${source}/${file} ${destination}/") ne 0);
}
}
copy_remote_if_necessary($ssh2, '/data/Directory1', '/data/Directory2', 'ABC.csv');