如果语句不起作用，则在Bash中进行正则表达式匹配

问题描述

下面是我正在处理的较大脚本的一小部分，但是下面给我带来了很多痛苦，这导致较大脚本的一部分无法正常运行.目的是检查变量是否具有匹配red hat或Red Hat的字符串值.如果是，则将变量名称更改为redhat.但这与我使用的正则表达式不太匹配.

The below is a small part of a bigger script I'm working on, but the below is giving me a lot of pain which causes a part of the bigger script to not function properly. The intention is to check if the variable has a string value matching red hat or Red Hat. If it is, then change the variable name to redhat. But it doesn't quite match the regex I've used.

getos="red hat"
rh_reg="[rR]ed[:space:].*[Hh]at"
if [ "$getos" =~ "$rh_reg" ]; then
  getos="redhat"
fi
echo $getos

任何帮助将不胜感激.

推荐答案

这里有多个问题需要解决

There are a multiple things to fix here

• bash在其[[扩展测试操作符中而不是在POSIX标准[测试操作符
中支持正则表达式模式匹配.
• 切勿引用我们的正则表达式匹配字符串. bash 3.2引入了兼容性选项compat31(在Bash 1.l中的新功能下) )，它将bash正则表达式的引用行为恢复为3.1，支持正则表达式字符串的引用.
• 修复正则表达式以使用[[:space:]]而不只是[:space:]

• bash supports regex pattern matching within its [[ extended test operator and not within its POSIX standard [ test operator
• Never quote our regex match string. bash 3.2 introduced a compatibility option compat31 (under New Features in Bash 1.l) which reverts bash regular expression quoting behavior back to 3.1 which supported quoting of the regex string.
• Fix the regex to use [[:space:]] instead of just [:space:]

所以就做

getos="red hat"
rh_reg="[rR]ed[[:space:]]*[Hh]at"
if [[ "$getos" =~ $rh_reg ]]; then
    getos="redhat"
fi;

echo "$getos"

或启用扩展外壳程序选项中的compat31选项

or enable the compat31 option from the extended shell option

shopt -s compat31
getos="red hat"
rh_reg="[rR]ed[[:space:]]*[Hh]at"
if [[ "$getos" =~ "$rh_reg" ]]; then
    getos="redhat"
fi
echo "$getos"
shopt -u compat31

但是不要用那些扩展程序操作符[[加上一个不带引号的正则表达式字符串变量，而不必弄乱这些shell选项.

But instead of messing with those shell options just use the extended test operator [[ with an unquoted regex string variable.

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