Bash中不区分大小写的正则表达式 [英] Case insensitive regex in Bash

问题描述

我想知道哪种方法更好地检查var（由用户在键盘上输入）是否以不区分大小写的方式与正则表达式匹配。我知道有一些不同的可能性。示例：我想要一个正则表达式，匹配一个空值和所有以下列表： Y ， N ， y ， n ，是，否，是，否

I want to know which method is better to check if a var (input by user on keyboard) matches with a regex in a case insensitive way. I know there are some different possibilities. Example: I want a regex matching an empty value and all of this list: Y, N, y, n, Yes, No, YES, NO

我搜索了不同的方法。不知道是否会更好。我会把它们中的一些给我用。

I searched looking different methods. Not sure if could be another better. I'll put a couple of them working for me.

• 第一个是有点棘手的，全部设置为大写比较：

• First one is a little "tricky" setting all to uppercase for the comparison:

#!/bin/bash
yesno="null" #any different value for initialization is valid
while [[ ! ${yesno^^} =~ ^[YN]$|^YES$|^NO$|^$ ]]; do
    read -r yesno
done

第二个正在使用 shopt -s nocasematch 。但不确定这样做之后是否可以还原，因为我不想为所有脚本设置它。

Second one is using shopt -s nocasematch. But not sure if after doing that it can be reverted because I don't want to set this for all the script.

#!/bin/bash
yesno="null" #any different value for initialization is valid
shopt -s nocasematch
while [[ ! ${yesno} =~ ^[yn]$|^yes$|^no$|^$ ]]; do
    read -r yesno
done

这些正则表达式可以通过任何方式得到改进吗？
是否有更好（更优雅）的方法？
在第二种方法上，是否有办法还原该设置？

Can these regex get improved in any way? Is there a better (more elegant) method? On second method, is there a way to revert that setting?

推荐答案

shopt 是一个好方法，因为您可以将最初输入的值保留在变量 yesno 中。

shopt is good approach as you are able to retain originally entered value in variable yesno.

您只需稍微重构一下正则表达式即可：

You can just refactor your regex a bit:

#!/bin/bash

yesno="null"

# set nocasematch option
shopt -s nocasematch

while [[ ! ${yesno} =~ ^([yn]|yes|no)?$ ]]; do
    read -r -p "Enter a yes/no value: " yesno
done

# unset nocasematch option
shopt -u nocasematch

# examine your variable
declare -p yesno

这篇关于Bash中不区分大小写的正则表达式的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！