How to kill a child process after a given timeout in Bash?

# Spawn a child process:
(dosmth) & pid=$!
# in the background, sleep for 10 secs then kill that process
(sleep 10 && kill -9 $pid) &

or to get the exit codes as well:

# Spawn a child process:
(dosmth) & pid=$!
# in the background, sleep for 10 secs then kill that process
(sleep 10 && kill -9 $pid) & waiter=$!
# wait on our worker process and return the exitcode
exitcode=$(wait $pid && echo $?)
# kill the waiter subshell, if it still runs
kill -9 $waiter 2>/dev/null
# 0 if we killed the waiter, cause that means the process finished before the waiter
finished_gracefully=$?

(As seen in: BASH FAQ entry #68: "How do I run a command, and have it abort (timeout) after N seconds?")

If you don't mind downloading something, use timeout (sudo apt-get install timeout) and use it like: (most Systems have it already installed otherwise use sudo apt-get install coreutils)

timeout 10 ping www.goooooogle.com

If you don't want to download something, do what timeout does internally:

( cmdpid=$BASHPID; (sleep 10; kill $cmdpid) & exec ping www.goooooogle.com )

In case that you want to do a timeout for longer bash code, use the second option as such:

( cmdpid=$BASHPID; 
    (sleep 10; kill $cmdpid) \
   & while ! ping -w 1 www.goooooogle.com 
     do 
         echo crap; 
     done )