How to automatically restart a screen -x program?

Question

Ubuntu 16.04 The program running under screen often crashes and I often have to manually reboot. How to set up auto-restart 3 times a day. ( I mean crontab to shut down it and run it again )

Thanks

Answer 1

HostFission's solution is good, but if you don't want to check if the program is running you can also kill it and start it like this:

Create a bash file with any name on it (like: restart.sh) and type this:

#/bin/bash

/usr/bin/screen -SX NameOfTheScreen quit;

/usr/bin/screen -S NameOfTheScreen /path/to/startscript;

-S sets the session name -X executes something on the session

Be careful not to use -S -X name, as this will name the session -X. Use - SX name instead.

Then you can set-up crontab to execute this file as many times as you want during the day.

crontab -e

* 3,6,9,12,15,18,21,0 * * * /path/to/restart.sh >> /path/to/logfile

Answer 2

You need to store the PID of the running process somewhere when it launches, and then later if it is still running send a SIGTERM to the process and wait for it to terminate. The below script will perform these actions.

PROGRAM=/bin/someProgram
PIDFILE=/var/run/someProgram.pid

if [ -f $PIDFILE ]; then
  PID = $(cat $PIDFILE)
  if [ -d /proc/$PID ] && [ "$(readlink -f /proc/$PID/exe)" == "$PROGRAM" ]; then
    echo -n "Shutting down..."
    kill $PID
    wait $PID
    echo "done."
  else
    echo "PID not found, program already terminated."
  fi
  rm $PIDFILE
fi

echo -n "Starting..."
$PROGRAM &
echo $! > $PIDFILE
echo "done."

Then just schedule this in cron to run every X hours.