shell之for、while循环
一、for循环# cat for.sh
#!/bin/bash
for i in `seq 1 10`; do
echo "$i"
done
通过这个脚本就可以看到for循环的基本结构:
for 变量名 in 循环的条件； do
command
done
# sh for.sh
1
2
3
4
5
6
7
8
9
10
例2：
# cat for2.sh
#!/bin/bash
for a in `ls`; do
echo "$a"
done
# sh for2.sh
case1.sh
case.sh
for2.sh
for3.sh
for.sh
if1.sh
if.sh
例3
# cat for3.sh
#!/bin/bash
for file in `vmstat`; do
echo "$file"
done
for i in `cd /shell && ls`; do
echo "$i"
done
引用系统命令需要加反引号，其他不用
# for i in 1 4 5 3 a a; do echo "$i"; done
1
4
5
3
a
a
二、while循环
# cat while.sh
#!/bin/bash
a=6
while [ $a -ge 1 ]; do
echo $a
a=$[$a-1]
done
while 循环格式也很简单:
while条件; do
command
done
# sh while.sh
6
5
4
3
2
1
例2
# cat while2.sh
#!/bin/bash
while :; do
seq 1 3
done
把循环条件拿一个冒号替代，这样可以做到死循环
# sh while2.sh
1
2
3
1
2
3
1
2
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