linux shell实现获取用户输入指定范围的单个字符的两种方法__letter_input_please_station1_root_

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linux shell实现获取用户输入指定范围的单个字符的两种方法

来源: 互联网发布时间：2014-10-14

本文导语: 方法一：代码如下:echo `echo {a..z}``echo {A..Z}` > /tmp/letterfilewhile read -p "please input a letter: " letterdo ((`awk -v var="$letter" 'BEGIN{print length(var)}'` == 1)) && grep -q $letter /tmp/tmpfile && breakdonerm -f /tmp/letterfileecho "you input letter $letter " [root@stati...

方法一：

代码如下:

echo `echo {a..z}``echo {A..Z}` > /tmp/letterfile
while read -p "please input a letter: " letter
do
    ((`awk -v var="$letter" 'BEGIN{print length(var)}'` == 1)) && grep -q $letter /tmp/tmpfile && break
done
rm -f /tmp/letterfile
echo "you input letter $letter "

[root@station1 ~]# cat a.sh

代码如下:

echo `echo {a..z}``echo {A..Z}` > /tmp/letterfile
while read -p "please input a letter: " letter
do
((`awk -v var="$letter" 'BEGIN{print length(var)}'` == 1)) && grep -q $letter /tmp/tmpfile && break
done
rm -f /tmp/letterfile
echo "you input letter $letter "

[root@station1 ~]# chmod +x a.sh
[root@station1 ~]# ./a.sh
please input a letter: 123
please input a letter: abc
please input a letter: 4
please input a letter: &
please input a letter: (
please input a letter: a
you input letter a
[root@station1 ~]#

最初使用expr length $letter 替代 wk -v var="$letter" 'BEGIN{print length(var)}'的，但是，当输入*等特殊字符时，会报错。
如下：
[root@station1 ~]# cat data

代码如下:

while read -p "please input a letter: " letter
do
((`expr length $letter` == 1)) && expr $letter : [[:alnum:]] > /dev/null && break
done
echo "you input letter $letter "

[root@station1 ~]# bash data
please input a letter: 123
please input a letter: abc
please input a letter: a
you input letter a
[root@station1 ~]# bash data
please input a letter: *
expr: 语法错误
data: line 3: ((: == 1: syntax error: operand expected (error token is "== 1")
please input a letter:

来看方法二：

代码如下:

while read -p "please input a letter: " letter
do
[[ `echo $letter | awk '/^[[:alpha:]]$/{print "1"}'` -eq 1 ]] && break
done
echo "you input letter $letter "

如下：
[root@station1 ~]# cat b.sh

代码如下:

while read -p "please input a letter: " letter
do
[[ `echo $letter | awk '/^[[:alpha:]]$/{print "1"}'` -eq 1 ]] && break
done
echo "you input letter $letter "

[root@station1 ~]# chmod +x b.sh
[root@station1 ~]# ./b.sh
please input a letter: *
please input a letter: abc
please input a letter: 234
please input a letter: )
please input a letter: T
you input letter T
[root@station1 ~]#