PHP runs Perl script from command line successfully but I get no output displayed

Question

I have a problem displaying the results of a Perl script that I am calling from my PHP webpage. The Perl script constantly monitors a socket and will display the output of this when run from the command line and also saves the output to a file. I know the Perl script is being called and running successfully as the text file is being updated but I do not get the output on the webpage as I was hoping for.

I have tried using the system(), exec(), passthru() and they all allow the Perl script to run but still with no output on the webpage so I am obviously missing something. Am I using the correct functions? Is there a parameter that I need to add to one of the above to push the output back to the webpage that calls the Perl script?

One example of what I have tried from the PHP manual pages:

<?php
exec('perl sql.pl', $output, $retval);
echo "Returned with status $retval and output:\n";
print_r($output);
?>

Edited to include output example as text instead of image as requested.

# perl sql.pl
Connecting to the PBX 192.168.99.200 on port 1752
 04/07 10:04:50             4788         4788 3256739                T912                                  200   2004788                                 A2003827 A

Dave Cross · Accepted Answer · 2021-04-07 15:10:25Z

2

I'm no PHP expert, but I guess that exec waits for the external program to finish executing before populating the $output and $return variables and returning.

You say that your sql.pl program "constantly monitors a socket". That sounds like it doesn't actually exit until the user closes it (perhaps with a Ctrl-C or a Ctrl-Z). So, presumably, your PHP code sits there waiting for your Perl program to exit - but it never does.

So I think there are a few approaches I'd investigate.

Does sql.pl have a command-line option that tells it to run once and then quit?
Does PHP have a way to send a Ctrl-C or Ctrl-Z to sql.pl a second or so after you've started it?
Does PHP have a way to deal with external programs that never end? Can you open a pipe to the external process and read output from it a line at a time?

answered Apr 7, 2021 at 15:10

Dave Cross

69.5k3 gold badges55 silver badges101 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Gerry Armstrong Over a year ago

Interesting, I think you are correct in saying the PHP is waiting for the script to exit which it is not doing as it is a constant connection to the host, I didn't think of that. I will look into the "open a pipe to the external process" as I need the Perl script to maintain its constant connection or I will lose data. Thanks for your suggestion Dave!

Dave Cross Over a year ago

@GerryArmstrong: It looks to me like you want popen.

Collectives™ on Stack Overflow

PHP runs Perl script from command line successfully but I get no output displayed

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related