On 2018-11-08 9:51 p.m., D&R wrote:
> I have tried several ways to connect to remote computer:
>
> $SERVER = qx{ssh -o ConnectTimeout=2 -o ControlPersist=yes $user\@$server
> "sudo hostname| cut -d "." -f1"}; chomp ($SERVER);
>
> but commands that have metacharacters, especially the single quote, I can not
> get to work.
>
> I can run the following from perl after ssh connection with single quotes
> included:
>
> $ssh = Net::OpenSSH->new("$user\@$server");
> $CMD = "grep -c alias cp='cp -f' /etc/bashrc";
> $fh = $ssh->pipe_out($CMD);
>
> while (<$fh>) {
> $OUTPUT .= $_;
> }
> chomp ($OUTPUT);
>
> and it works.
>
> But if add 'sudo' for cases where I need to read a file that the login user
> does not have permissions for -- I can not get it to work.
>
> I have searched and tried a number of recommendations and it either fails with
> a permission error or locks up or gives grep errors.
>
> Thanks in advance,
>
> David
Hi David,
We have a program that does a lot of SSH'ing, and wrote a perl module
(as part of a larger project). We're using Net::SSH2 as the back-end. We
also use rsync (over ssh) to move files around.
I can't speak to your specific issue, but perhaps our code can give
you some ideas?
https://github.com/digimer/anvil/blob/master/Anvil/Tools/Remote.pm
There, look at the 'call()' method (line 258 in the current commit).
There is a bunch of sanity checking you can probably ignore, with the
most interesting bit starting at (current) line 414.
Here is a condensed version (obviously untested) to hopefully make the
key steps easier to follow (our program uses translation so the user
messages are not immediately obvious in the source).
====
$ssh_fh = Net::SSH2->new(timeout => 1000);
if (not $ssh_fh->connect($target, $port))
{
# examine '$@' for why it failed.
die;
}
if (not $ssh_fh->auth_password($remote_user, $password))
{
# Failed with password, try again in case passwordless ssh works
if ($ssh_fh->auth_publickey($user, $public_key, $private_key))
{
# That worked.
}
else
{
# No luck
die;
}
}
else
{
# Connected with password successfully
}
# We need to open a channel every time for 'exec' calls. We want to keep
# blocking off, but we need to enable it for the channel() call.
$ssh_fh->blocking(1);
my $channel = $ssh_fh->channel() or $ssh_fh->die_with_error;
if (not $channel)
{
# Try again a few times and die if none work...
}
$ssh_fh->blocking(0);
$channel->exec("$shell_call");
my @poll = {
handle => $channel,
events => [qw/in err/],
};
# We'll store the STDOUT and STDERR data here.
my $stdout = "";
my $stderr = "";
# Now collect the data.
while(1)
{
$ssh_fh->poll(250, \@poll);
# Read in anything from STDOUT
while($channel->read(my $chunk, 80))
{
$stdout .= $chunk;
}
while ($stdout =~ s/^(.*)\n//)
{
my $line = $1;
push @{$stdout_output}, $line;
}
# Read in anything from STDERR
while($channel->read(my $chunk, 80, 1))
{
$stderr .= $chunk;
}
while ($stderr =~ s/^(.*)\n//)
{
my $line = $1;
push @{$stderr_output}, $line;
}
# Exit when we get the end-of-file.
last if $channel->eof;
}
====
--
Digimer
Papers and Projects: https://alteeve.com/w/
"I am, somehow, less interested in the weight and convolutions of
Einstein’s brain than in the near certainty that people of equal talent
have lived and died in cotton fields and sweatshops." - Stephen Jay Gould
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