[root@xieqichao ~]# cat > test15.sh#!/bin/shecho -n "Enter your input: "read input
#1. 事实上,这里的巧妙之处就是先用sed替换了非法部分,之后再将替换后的结果与原字符串比较。这种写法也比较容易扩展。
parsed_input=`echo $input |sed's/[^[:alnum:]]//g'`if["$parsed_input"!="$input"];thenecho"Your input must consist of only letters and numbers."elseecho"Input is OK."fi
CTRL+D
[root@xieqichao ~]# ./test15.sh
Enter your input: hello123
Input is OK.
[root@xieqichao ~]# ./test15.sh
Enter your input: hello world
Your input must consist of only letters and numbers.
```