Bash script to start process, wait random, kill process, restart

Question

I\'m an absolute beginner and am trying to create a bash script to randomize the start and exit of a command line app. I plan to autostart the script on boot (Crunchbang) after

Answer 1

Try this code for your randomizer.sh

min_val=60
range=150
while true ; do
    run_this_command &
    last_pid=$!
    sleep $[ ( $RANDOM % $range ) + $min_val ]
    { [ "$(ps -p $last_pid -o comm= )" ] && \
      [ "$(ps -p $last_pid -o comm= )" = run_this_command ]; 
    } && { kill -KILL $last_pid ;}
done

Some notes:

1. Rather than using the exec statement. You can accomplish what your trying to do more simply by staying inside a while loop. The randomiser.sh I present is only read from the hard drive once.
2. The code { [ condition ] && { command ;} && command runs faster than if [ condition ]; then command, else command; fi
3. With the variable $last_pid assigned to the value of $!, the command ps -p $last_pid -o comm= will spit out the name of the process with the PID of $last_pid. If there is no PID with that value then its exist code is 1.

---

Amended to meet the additional random wait period before start requirement:

# Minimum and range values for random Wait before start in seconds
MinA=60;RangeA=150 
# Minimum and range values for random Wait before kill in seconds
MinB=60; RangeB=150 # 
while true ; do
    sleep $[ ( $RANDOM % $RangeA ) + $MinA ] 
    run_this_command &
    last_pid=$!
    sleep $[ ( $RANDOM % $RangeB ) + $MinB ] 
    { [ "$(ps -p $last_pid -o comm= )" ] && \
      [ "$(ps -p $last_pid -o comm= )" = run_this_command ]
    } && \{ kill -KILL $last_pid ;}
done