需求：要求獲取用戶輸一個字符a-zA-Z：

方法一：

復制代碼 代碼如下:

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

復制代碼 代碼如下:

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，當輸入*等特殊字符時，會報錯。

如下：

[root@station1 ~]# cat data

復制代碼 代碼如下:

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: 語法錯誤

data: line 3: ((: == 1: syntax error: operand expected (error token is "== 1")

please input a letter:

來看方法二：

復制代碼 代碼如下:

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

復制代碼 代碼如下:

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 ~]#

總結

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