linuxSHELL学习之for、while、until
一、for命令用于循环操作
1、读取列表中的复杂值
*使用转义字符（反斜杠符号）来转义单引号
*使用双引号来定义使用单引号的值
[root@t1 ~]# cat t20.sh
#!/bin/bash
for test in I don't know if this'll work
do
echo "word:$test"
done
[root@t1 ~]# ./t20.sh
word:I
word:dont know if thisll ---不是我们想要的结果
word:work
[root@t1 ~]# cat t21.sh
#!/bin/bash
for test in I don\'t know if "this'll" work --使用 "\"转义单引号，使用双引号定义使用单引号的值
do
echo "word:$test"
done
[root@t1 ~]# ./t21.sh
word:I
word:don't
word:know
word:if
word:this'll
word:work
2、运行多字值，for循环认为每个值都用空格分开，如果有包含空格的数据值，就会遇到另一个问题：又包含空格的值就必须用双引号引起来使用。
[root@t1 ~]# cat t22.sh
#!/bin/bash
for test in New Hampshire New York New Mexico
do
echo "Now going to $test"
done
[root@t1 ~]# ./t22.sh ---不是想要的结果
Now going to New
Now going to Hampshire
Now going to New
Now going to York
Now going to New
Now going to Mexico
[root@t1 ~]# cat t23.sh
#!/bin/bash
for test in "New Hampshire" "New York" "New Mexico" ---使用双引号之后得到想要的结果
do
echo "Now going to $test"
done
[root@t1 ~]# ./t23.sh
Now going to New Hampshire
Now going to New York
Now going to New Mexico
3、从变量读取列表
[root@t1 ~]# cat t24.sh
#!/bin/bash
