Shell script for loop, break out loop, continue end this loop

20.10 for Loop

• Syntax: for variable name in condition; Do ...; Done

;案例1[[email protected] shell]# cat for.sh#!/bin/bashsum=0for i in `seq 1 100`do    sum=$[$sum+$i]doneecho $sum#输出的结果[[email protected] shell]# sh for.sh 5050

• File list loop

[[email protected] shell]# cat for2.sh #!/bin/bashcd /etc/for a in `ls /etc/`do    if [ -d $a ]    then        ls -d $a    fidone#for循环是以空格、回车符作为分割符分割。

20.11-20.12 while loop

• syntax while condition; Do ...; Done

;案例1[[email protected] shell]# cat while.sh #!/bin/bashwhile :do    load=`w|head -1 |awk -F ‘load average: ‘ ‘{print $2}‘| cut -d . -f1`    if [ $load -gt 10 ]    then        top|mail -s "load is high:$load" [email protected]    fi    sleep 30done;案例2[[email protected] shell]# cat while2.sh #!/bin/bashwhile :do  read -p "Please input a number:" n  if [ -z "$n" ]  then      echo "You did not enter the number."      continue  fi  n1=`echo $n|sed ‘s/[0-9]//g‘`  if [ ! -z "$n1" ]  then      echo "You can only enter a pure number."      continue  fi  breakdoneecho $n

20.13 break jump out of the loop

[[email protected] shell]# cat break.sh #!/bin/bashfor i in `seq 1 5`do  echo $i  if [ $i -eq 3 ]  then      break  fi  echo $idoneecho aaaaaa

20.14 continue ends this cycle

[[email protected] shell]# cat continue.sh #!/bin/bashfor i in `seq 1 5`do  echo $i  if [ $i -eq 3 ]  then      continue  fi  echo $idoneecho $i

20.15 exit exits the entire script

[[email protected] shell]# cat exit.sh #!/bin/bashfor i in `seq 1 5`do  echo $i  if [ $i -eq 3 ]  then      exit  fi  echo $idoneecho $i

Shell script for loop, break out loop, continue end this loop