在外壳程序中仅过滤三个字符 [英] Filter only three characters in shell

问题描述

我正在尝试在shell中解析命令，并且在一个选项中，如果字符串具有"r"，"w"，"x"，其中之一，全部，我想保存到变量中，或混合，但只有这三个.不允许其他字符！

I am trying to parse a command in shell, and in one of the options I want to save in a variable if a string has "r", "w", "x", one of those, all of them, or a mix, but only these three. No other characters should be allowed!

我尝试了以下情况:

 $2 in *r*) ;; *w*) ;; *x*) ;; *  ) echo no ;;
esac

但是在这种情况下，如果写入了zr，它将通过，因为它具有"r".只要它具有这三个，三个或两个(任何一种组合)但没有其他字符，我只想让它通过.

But in this case if there is written zr it will pass, as it has an "r". I only want to make it pass as long as it has one of these three, the three of them, or two of them (any kind of combination), but no other characters.

推荐答案

在BASH中，您可以使用正则表达式进行此检查，如下所示:

In BASH you can use regex for this check like this:

re='^[rwx]+$'

s='rw'
[[ $s =~ $re ]] && echo "yes" || echo "no"
yes

s='zr'
[[ $s =~ $re ]] && echo "yes" || echo "no"
no

正则表达式^[rwx]+$允许1个或多个r或w或x字母.

Regex ^[rwx]+$ will allow 1 or more of r or w or x letters.

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