利用trap ping c类网络:
let LINENUME=0
while getopts ":n" SWITCH; do
 case $SWITCH in
n)
let LINENUME=1
;;
\?) echo " no line"
    exit 1
;;
esac
done
shift $[$OPTIND-1]
  let i=1
 while read line; do
if [ $LINENUME -eq 1 ]; then
  echo "$i $line"
 let i++
 else
  echo "$line"
fi
done < $1