How to check if the change command is success in telnet

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

Fellow Monks,
I am using telnet for changing the directory in the remote server using my perl script.This is the line for changing the directory,
$rad = $telobj -> cmd ("cd /usr/local/etc/httpd/logs");
I have to check if the change command is executed successfully,then proceed to next block of statements, Eg.

if($rad){
//block of statement
}else{
print"Directory not found\n";
}
[download]

But the $rad value is alwasy found as 1 even if the command is failing.How to solve this monks,
Thanks.

Comment on How to check if the change command is success in telnet Download Code

Replies are listed 'Best First'.
Re: How to check if the change command is success in telnet by shmem (Chancellor) on Jun 27, 2006 at 07:28 UTC
The `cmd` method of a `telnet` object returns a list, so if you have a scalar at the left of your assignment operator ( = ), you evaluate the returned list in scalar context, and the number of elements of the list will be assigned to `$rad`. To assign the first element of that list to `$rad` do the following: `($rad) = $telobj -> cmd ("cd /usr/local/etc/httpd/logs");` [download] This way the left hand side (lhs) of the assignment operator is a list, and its first element - `$rad` - will be assigned the first value of the list returned by the `cmd` method. Note that `$rad` is enclosed in parens, which makes the lhs a list statement. To check whether the previous `cd` command has been succesful, you could do: `($rad) = $telobj->("pwd"); if($rad eq '/usr/local/etc/httpd/logs') { print "cd command successful. working directory is $rad\n"; } else { print "cd command failed. working directory is $rad\n"; }` [download] But it's even easier in fact. The `cd` shell command doesn't return anything if successful, only on failure. So, you could just say `($rad) = $telobj -> cmd ("cd /usr/local/etc/httpd/logs"); if($rad) { die "Can't change directory: $rad\n"; }` [download] --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re: How to check if the change command is success in telnet
by shmem (Chancellor) on Jun 27, 2006 at 07:28 UTC

cmd

telnet

scalar

evaluate the returned list in scalar context

number of elements

$rad

To assign the first element of that list to $rad do the following:

($rad) = $telobj -> cmd ("cd /usr/local/etc/httpd/logs");
[download]

This way the left hand side (lhs) of the assignment operator is a list, and its first element - $rad - will be assigned the first value of the list returned by the cmd method. Note that $rad is enclosed in parens, which makes the lhs a list statement.

To check whether the previous cd command has been succesful, you could do:

($rad) = $telobj->("pwd");
if($rad eq '/usr/local/etc/httpd/logs') {
    print "cd command successful. working directory is $rad\n";
} else {
    print "cd command failed. working directory is $rad\n";
}
[download]

cd

($rad) = $telobj -> cmd ("cd /usr/local/etc/httpd/logs");
if($rad) {
    die "Can't change directory: $rad\n";
}
[download]

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

[reply]
[d/l]
[select]