perl exec screen with parameters

Question

If I run the following:

system("screen -dmS $screenname");

it works as it should be but when I try to run a screen from perl and to execute a command (in this case tcpreplay) with some extra arguments it doesn't run as it's supposed to.

system("screen -dmS $screenname -X stuff \"`printf \"tcpreplay --intf1=eth0 s.cap\\r\"`\" ");

What am I doing wrong here?

Answer 1

Simo A's answer is probably right with regards to the issue, but I like to use the following when working with screen opposed to using the -X flag. Explicitly telling it the command language interpreter.

Why use -c you ask?

If the -c option is present, then commands are read from string. If there are arguments after the string, they are assigned to the positional parameters, starting with $0.

system("screen -dmS $screenname sh -c 'PRETTY MUCH ANYTHING WORKS'");

I figured I'd shared as I run alot of Perl system commands and the above always works for screen commands.

Answer 2

Try replacing single \" with \\\". That should do the trick.

Consider the same issue here:

system ("echo Quotation marks: \\\"here\\\" but \"not here\". ");

The output from the former line of code is: Quotation marks: "here" but not here.

Answer 3

Taking Simo A's answer as a starting point, I would use q( ) rather than " ".

system ( q(echo Quotation marks: \"here\" but "not here". ));

This means you don't need to escape the quote twice.