0001 Alarm handling:
0002
0003
0004 #!/bin/bash
0005
0006 #Time to wait for stuck processes before killing them
0007 export ALARMTIME=30
0008
0009 PARENTPID=$$
0010
0011 exit_timeout() {
0012 echo "Alarm signal received : killing all children"
0013 for pid in ${CHILDPIDS[@]}; do
0014 kill $pid >/dev/null 2>&1
0015 done
0016 exit
0017 }
0018
0019 CHILDCOUNT=0
0020
0021 for server in alice bob charlie; do
0022 CHILDCOUNT=$CHILDCOUNT+1
0023 echo "Running command on $server:"
0024 ssh $server "uname -a" &
0025 CHILDPIDS[$CHILDCOUNT]=$!
0026 done
0027
0028 #Prepare to catch SIGALRM, call exit_timeout
0029 trap exit_timeout SIGALRM
0030
0031 #Sleep in a subprocess, then signal parent with ALRM
0032 (sleep $ALARMTIME; kill -ALRM $PARENTPID) &
0033 #Record PID of subprocess
0034 ALARMPID=$!
0035
0036 #Wait for child processes to complete normally
0037 wait ${CHILDPIDS[*]}
0038
0039 echo "Alarm never reached, children exited cleanly."
0040 #Tidy up the Alarm subprocess
0041 kill $ALARMPID
0042
0043
