shell循环

shell脚本经常需要用到循环。在提示符下直接键入help将看到下面所有shell循环命令的基本用法。键入man bash会获得更多更详细相关信息。

1、for循环

for ((i=1;i<11;i++))
#for i in {01..10}
do
#mkdir `printf data"%02d\n" $i`;
mkdir $(printf data"%03d\n" $i)
done

2、while循环

#!/bin/sh

i=1
#while [[ i -lt 11 ]];
#while [ $i -lt 11 ];
while [ $i < 11 ];
do
echo $i;
#((i=i+1));
let i=i+1
done

3、while infinite loops

#!/bin/sh

i=1;
while :;
do
echo $i;
((i=i+1));
if [[ i -gt 10 ]];then
break;
fi
done

4、until循环
#!/bin/sh

x=1
until [ $x -ge 11 ];
do
echo $x
let x=x+1;
#x=`expr $x + 1`
done

5、until example
#bin/bash
i=1
s=0
until [[ i -gt 30 ]];
do
((s=s+i));
((i=i+1));
done

echo "The result is $s"

6、Here is a sample shell code to calculate factorial using while loop阶乘:
#!/bin/bash
counter=$1
factorial=1
while [ $counter -gt 0 ]
do
factorial=$(( $factorial * $counter ))
counter=$(( $counter - 1 ))
done
echo $factorial

To run just type:
$ chmod +x script.sh
$ ./script.sh 5
Output: 120
7、select循环的典型例子
vi select.sh
#!/bin/sh
echo "What is your favourite OS?"

select var in "Linux" "Windows" "Unix" "Other";
do
break;
#select本身就是一个循环，break是当选择后，就跳出循环
done

echo "You have selected $var"

#sh select.sh
What is your favourite OS?
1) Linux
2) Windows
3) Unix
4) Other
#? 1
You have selected Linux
8, select+while
#!/bin/sh

while echo "display current netconfig:"
do
select cmd in "ifconfig -a" "route" "netstat2" "quit"
do

case $cmd in
"ifconfig -a")
/sbin/ifconfig -a;;
"route")
netstat -rn;;
"netstat2")
netstat -nat|grep :80|awk '{print awk $NF}'|sort|uniq -c|sort -n;;
"quit")
exit 0;;
*)
continue;;
esac

break
done
done

9、calculate

((i=i+1));
let i=i+1;
x=$(( $x + 1 ))
x=`expr $x + 1`

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