関数を呼び出し、値を変数に保存します。

pid=`ps -ef | grep wcm2_wcm2appwlx | awk '$0!~/grep/ && $2~/[0-9]/{print $2}'`
for I in 1 2 3 4 5
do
sts=$(check)
  if [$sts eq / true/]
  then
        echo $I
        slp
  else
        break              #Abandon the loop.
  fi
done
slp(){
echo "sleep is executing "
}
check(){
if ps -p $pid > /dev/null
then
   echo " Backup Script is running with $PID "
   return true
fi
}