一、for循环
语法：for 变量名 in 条件; do …; done
案例1：
#!/bin/bash
sum=0
for i in `seq 1 100`
do
sum=$[$sum+$i]
echo $i
done
echo $sum
案例2：文件列表循环
#!/bin/bash
cd /etc/
for a in `ls /etc/`
do
if [ -d $a ]
then
ls -d $a
fi
done
二、while循环
语法 while 条件; do … ; done
案例1：
#!/bin/bash
while :
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: $load" asldkfls@11.com
fi
sleep 30
done
案例2：
#!/bin/bash
while :
do
read -p "Please input a number: " n
if [ -z "$n" ]
then
echo "you need input sth."
continue
fi
n1=`echo $n|sed 's/[0-9]//g'`
if [ -n "$n1" ]
then
echo "you just only input numbers."
continue
fi
break
done
echo $n
三、break跳出循环
#!/bin/bash
for i in `seq 1 5`
do
echo $i
if [ $i == 3 ]
then
break
fi
echo $i
done
echo aaaaaaa
四、continue结束本次循环
忽略continue之下的代码，直接进行下一次循环
#!/bin/bash
for i in `seq 1 5`
do
echo $i
if [ $i == 3 ]
then
continue
fi
echo $i
done
echo $i
五、exit退出整个脚本
#!/bin/bash
for i in `seq 1 5`
do
echo $i
if [ $i == 3 ]
then
exit
fi
echo $i
done
echo aaaaaaa
扩展
select用法 http://www.apelearn.com/bbs/thread-7950-1-1.html