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Top Forums Shell Programming and Scripting Read input while another command is running && Post 302901779 by cnamejj on Thursday 15th of May 2014 02:47:34 PM
Old 05-15-2014
If that's the entire script and you just want to run "tshark" for 10 seconds, then wait 5 seconds and do it again. Then if you can accept typing "^c" instead of "q" to stop it, the whole thing can probably be reduced to this:

Code:
while[ 1 ]
do
    timeout 10s tshark -l -i eth0
    sleep 5
done

You may have to hit "^c" twice to stop the script sometimes.

If you want to keep the current logic, where you hit "q" to stop and that also stops the "tshark", then you need to do something more sophisticated.

You'll have to run "tshark" as a background process, capture the PID in the shell script, then if "q" is entered kill that PID before exiting.

The other problem you'll have is that the while loop will cycle every 5 seconds (since you're using "-t 5" on the read), but the "tshark" subprocess will run for 10 seconds. So you'll wind up with an ever increasing number of "tshark" processes running in parallel.

If you make the timeout on the "read" longer than the timeout on the "tshark" calls that won't be a problem, but it will also mean the pause between "tshark" runs will be longer than 5 seconds.

If you want to fix THAT problem, then you need to add logic to the shell script to make sure that you only have one "tshark" running at once.

So what to do depends on how big of a hole you want to dig for yourself. Smilie
 

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service(8)						      System Manager's Manual							service(8)

NAME
service - run a System V init script SYNOPSIS
service SCRIPT COMMAND [OPTIONS] service --status-all service --help | -h | --version DESCRIPTION
service runs a System V init script in as predictable environment as possible, removing most environment variables and with current working directory set to /. The SCRIPT parameter specifies a System V init script, located in /etc/init.d/SCRIPT. The supported values of COMMAND depend on the invoked script, service passes COMMAND and OPTIONS it to the init script unmodified. All scripts should support at least the start and stop commands. As a special case, if COMMAND is --full-restart, the script is run twice, first with the stop command, then with the start command. service --status-all runs all init scripts, in alphabetical order, with the status command. If the init script file does not exist, the script tries to use legacy actions. If there is no suitable legacy action found and COMMAND is one of actions specified in LSB Core Specification, input is redirected to the systemctl. Otherwise the command fails with return code 2. FILES
/etc/init.d The directory containing System V init scripts. ENVIRONMENT
LANG, TERM The only environment variables passed to the init scripts. SEE ALSO
chkconfig(8), ntsysv(8), systemd(1), systemctl(8), systemd.service(5) Jan 2006 service(8)
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