但是，当输入*等特殊字符时，会报错。

需求：要求获取用户输一个字符a-zA-Z： 方法一： 复制代码 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 $letter [root@station1 ~]# cat a.sh 复制代码 代码如下: echo `echo {a..z}``echo {A..Z}` /tmp/letterfile while read -p please input a letter: letter do ((`awk -v var=$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。

如下： [root@station1 ~]# cat data 复制代码 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： 复制代码 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 复制代码 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 ~]# ，。