Trying to capture STDOUT with PERL

DBelcher · 10-16-2008, 11:09 PM

Given the following function:

Code:

sub execute($) {
    local $response = qx!$_[0]!;
    local $result = ($? >> 8);

    return ($result,$response);
}

If called with the following argument:

Code:

($Result,$Response) = execute("iwconfig");

I would expect $Response to contain the STDOUT and $Result to contain the STDERR. But that is only partially true. Within the terminal I see the following print out

Code:

lo        no wireless extensions.

etho      no wireless extensions.

wifi0     no wireless extensions.

and when I step through the code, I see that $Response has the rest of the output from the "iwconfig" command:

Code:

ath0        IEE 802.11g ESSID:""  Nickname:""
...etc...

The question that I have is, why can't I capture ALL of the STDOUT? Why does some still escape and get printed to the screen regardless? I've tried backticks, system(), and even piping the output to a file...but none of them work completely to mask all STDOUT from getting printed to the screen. In case you are wonderring, my intention is to create a function that can silently run commands in the background without interfering with main execution by printing crap on the screen. Any ideas?

Thanks,
DBelcher

ciotog · 10-16-2008, 11:24 PM

Those messages are going to STDERR.

Have a gander at this:
http://perldoc.perl.org/perlfaq8.htm...nal-command%3f

DBelcher · 10-16-2008, 11:33 PM

Awesome...I had no idea! I thought STDERR was merely a numeric exit code and didn't realize it could be text. I decided to just use the bash redirection to add the STDERR to STDOUT and capture it that way, like so:

Code:

local $response = qx!$_[0] 2>&1!;

Thank you very much!
DBelcher