timer follow a PID

reporting/timer

@@ -4,6 +4,7 @@ function helpexit() {
     echo "Simple Timer."
     echo '$PREFIX is printed before the time'
     echo '$POSTFIX is printed after the time'
+    echo '$TIMERPID is a PID number. When the process ends, timer ends.'
     echo 'Reset timer with kill -10'
     echo '
 
@@ -14,6 +15,11 @@ function helpexit() {
 #  sleep 10; kill -10 %1; sleep 5; kill %1
 #
 #  PREFIX=$'"'"'\033[33;1m'"'"' POSTFIX=$'"'"'\033[0m'"'"' timer | sleep 5
+#
+#  sleep 4 &
+#  p=$!
+#  TIMERPID=$p timer &
+#  sleep 10
 '
     exit
 }
@@ -37,6 +43,7 @@ function displaytime {
 }
 
 function finish_up {
+  echo "Timer terminated" >&2
   displaytime "$SECONDS" >&2
   echo "" >&2
   exit
@@ -60,6 +67,9 @@ while true; do
   # if stdout is pipe, print time there
   # if pipe dies, timer dies too
   if [[ ! -t 1 ]]; then displaytime "$SECONDS"; fi
+  if [[ -n "$TIMERPID" ]]; then
+    kill -0 "$TIMERPID" 2>/dev/null || { exit; }
+  fi
   sleep 1
 done