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


Hello everyone... I am having a hell of a time trying to extract (using the cat unix function)
a file into an array. The snippet below returns an empty array. The input_log shows the actions are performing accordingly. The program was timeing out at the cat line, I rectified this by forcing the Errmode to return. Anyones insight is greatly appreciated.

$telnetobj = new Net::Telnet->new(Timeout => 120,
                                  Prompt=> '/X>/',
                                  Binmode    => 1,
                                  Errmode   => "return",
                                  Output_record_separator => "\n",
                                  Input_log  => $file_log);
$telnetobj->open($HOH{$JOB}{Node});
$telnetobj->prompt('/login: /');
$telnetobj->print(''); #add one <CR> to display login
my $loginpmpt = '/login: /';
$telnetobj->waitfor($loginpmpt);
$telnetobj->print($HOH{$JOB}{'Login'});
$telnetobj->waitfor('/Password:/');
$telnetobj->print($HOH{$JOB}{"Password"});

$telnetobj->prompt;
$telnetobj->waitfor(/X>/);
$telnetobj->prompt();
$telnetobj->print("who");
$telnetobj->put();
my @stuff = $telnetobj->cmd("cat $filename");
$telnetobj->waitfor(/X>/);
$telnetobj->close; ## close telnet session");

[download]

holli fixed formatting

jdporter fixed formatting even more

Replies are listed 'Best First'.
Re: unix cat
by davidrw (Prior) on Feb 09, 2006 at 14:01 UTC
    Your closing </code> tag is missing the slash...

    Is this the exact code you're running? The 'cat' line is missing a " ...

    Do you have to use Telnet for this? http, ftp, scp (bunches of modules for each) would be much easier and more robust (if $filename has a 'X>' in it you're going to lose data).
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      That was a typo... The cat line does include the closing ".
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Re: unix cat
by Roy Johnson (Monsignor) on Feb 09, 2006 at 15:10 UTC
    Are you sure $filename is set, contains no spaces, and that a file by that name exists? The waitfor call should be unnecessary after a cmd according to Net::Telnet docs.
    Caution: Contents may have been coded under pressure.
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[d/l]
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Re: unix cat
by jcc (Sexton) on Feb 09, 2006 at 16:30 UTC
    Since you're not changing directories, I assume that your file is in the user's home directory - or $filename contains an explicit path to the file with valid seperators etc.

    I also echo the sentiment that telnet is the wrong tool for this job... just grab the file with Net::FTP and operate on it locally.
[reply]

      Thank you for everyones remarks. Further investigation found that the Telnet module needs to read in blocks when trying to populate a local variable...Should have researched this a little further before posting. Thanks again.
       ## Make sure prompt won't match anything in send data.
$prompt = "_funkyPrompt_";
$host->prompt("/$prompt\$/");
$host->cmd("set prompt = '$prompt'");

    ## Get size of file.
    ($line) = $host->cmd("/bin/ls -l $filename");
    ($size_bsd, $size_sysv) = (split ' ', $line)[3,4];
    if ($size_sysv =~ /^\d+$/) {
        $size = $size_sysv;
    }
    elsif ($size_bsd =~ /^\d+$/) {
        $size = $size_bsd;
    }
    else {
        die "$filename: no such file on $hostname";
    }

    ## Start sending the file.
    binmode STDOUT;
    $host->binmode(1);
    $host->print("/bin/sh -c 'stty raw; cat $filename'");
    $host->getline;    # discard echoed back line

    ## Read file a block at a time.
    $num_read = 0;
    $prevblock = "";
    $start_time = time;
    while (($block = $host->get) and $block !~ /$prompt$/o)) {
        if (length $block >= length $prompt) {
            print $prevblock;
            $num_read += length $prevblock;
            $prevblock = $block;
        }
        else {
            $prevblock .= $block;
        }

    }
    $host->close;

    ## Print last block without trailing prompt.
    $prevblock .= $block;
    $prevblock =~ s/$prompt$//;
    print $prevblock;
    $num_read += length $prevblock;
    die "error: expected size $size, received size $num_read\n"
        unless $num_read == $size;

    ## Print totals.
    $total_time = (time - $start_time) || 1;
    $k_per_sec = ($size / 1024) / $total_time;
    $k_per_sec = sprintf "%3.1f", $k_per_sec;
    warn("$num_read bytes received in $total_time seconds ",
         "($k_per_sec Kbytes/s)\n");

      [download]

      Edited by planetscape - added code tags

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