Just use /proc to see if a process is running

tools/killall5.in

@@ -39,7 +39,7 @@ get_procs_to_kill() {
 
 pids_exist() {
 	for i in "$@"; do
-		if kill -0 "$i" 2>/dev/null; then
+		if [[ -d "/proc/$i" ]]; then
 			return 0
 		fi
 	done