bash 正则表达式带引号？

Question

下面的代码

number=1
if [[ $number =~ [0-9] ]]
then
  echo matched
fi

作品。但是，如果我尝试在正则表达式中使用引号，它就会停止：

number=1
if [[ $number =~ "[0-9]" ]]
then
  echo matched
fi

我试过 "\[0-9\]", ， 也。我缺少什么？

有趣的是， bash 高级脚本编写指南 建议这应该有效。

bash 版本 3.2.39。

Answer 1

已更改 3.1 至 3.2 之间. 。猜猜高级指南需要更新。

这是自Bash-3.1发行以来添加到Bash-3.2中添加到Bash-3.2的新功能的简短描述。与往常一样，手动页面（DOC/BASH.1）是寻找完整描述的地方。

1. Bash 中的新功能

剪断

F。引用字符串参数到[[命令的=〜运算符现在强迫字符串匹配，就像其他模式匹配操作员一样。

遗憾的是，这将破坏使用脚本的现有引用，除非您有能力将模式存储在变量中并直接使用它们而不是正则表达式。下面的例子。

$ bash --version
GNU bash, version 3.2.39(1)-release (i486-pc-linux-gnu)
Copyright (C) 2007 Free Software Foundation, Inc.
$ number=2
$ if [[ $number =~ "[0-9]" ]]; then echo match; fi
$ if [[ $number =~ [0-9] ]]; then echo match; fi
match
$ re="[0-9]"
$ if [[ $number =~ $re ]]; then echo MATCH; fi
MATCH

$ bash --version
GNU bash, version 3.00.0(1)-release (i586-suse-linux)
Copyright (C) 2004 Free Software Foundation, Inc.
$ number=2
$ if [[ $number =~ "[0-9]" ]]; then echo match; fi
match
$ if [[ "$number" =~ [0-9] ]]; then echo match; fi
match

Answer 2

Bash 3.2 引入了一个兼容性选项 compat31，它将 bash 正则表达式引用行为恢复到 3.1

没有 compat31:

$ shopt -u compat31
$ shopt compat31
compat31        off
$ set -x
$ if [[ "9" =~ "[0-9]" ]]; then echo match; else echo no match; fi
+ [[ 9 =~ \[0-9] ]]
+ echo no match
no match

对于compat31：

$ shopt -s compat31
+ shopt -s compat31
$ if [[ "9" =~ "[0-9]" ]]; then echo match; else echo no match; fi
+ [[ 9 =~ [0-9] ]]
+ echo match
match

补丁链接：http://ftp.gnu.org/gnu/bash/bash-3.2-patches/bash32-039

Answer 3

GNU bash，版本 4.2.25(1)-release (x86_64-pc-linux-gnu)

字符串匹配和正则表达式匹配的一些示例

    $ if [[ 234 =~ "[0-9]" ]]; then echo matches;  fi # string match
    $ 

    $ if [[ 234 =~ [0-9] ]]; then echo matches;  fi # regex natch 
    matches


    $ var="[0-9]"

    $ if [[ 234 =~ $var ]]; then echo matches;  fi # regex match
    matches


    $ if [[ 234 =~ "$var" ]]; then echo matches;  fi # string match after substituting $var as [0-9]

    $ if [[ 'rss$var919' =~ "$var" ]]; then echo matches;  fi   # string match after substituting $var as [0-9]

    $ if [[ 'rss$var919' =~ $var ]]; then echo matches;  fi # regex match after substituting $var as [0-9]
    matches


    $ if [[ "rss\$var919" =~ "$var" ]]; then echo matches;  fi # string match won't work

    $ if [[ "rss\\$var919" =~ "$var" ]]; then echo matches;  fi # string match won't work


    $ if [[ "rss'$var'""919" =~ "$var" ]]; then echo matches;  fi # $var is substituted on LHS & RHS and then string match happens 
    matches

    $ if [[ 'rss$var919' =~ "\$var" ]]; then echo matches;  fi # string match !
    matches



    $ if [[ 'rss$var919' =~ "$var" ]]; then echo matches;  fi # string match failed
    $ 

    $ if [[ 'rss$var919' =~ '$var' ]]; then echo matches;  fi # string match
    matches



    $ echo $var
    [0-9]

    $ 

    $ if [[ abc123def =~ "[0-9]" ]]; then echo matches;  fi

    $ if [[ abc123def =~ [0-9] ]]; then echo matches;  fi
    matches

    $ if [[ 'rss$var919' =~ '$var' ]]; then echo matches;  fi # string match due to single quotes on RHS $var matches $var
    matches


    $ if [[ 'rss$var919' =~ $var ]]; then echo matches;  fi # Regex match 
    matches
    $ if [[ 'rss$var' =~ $var ]]; then echo matches;  fi # Above e.g. really is regex match and not string match
    $


    $ if [[ 'rss$var919[0-9]' =~ "$var" ]]; then echo matches;  fi # string match RHS substituted and then matched
    matches

    $ if [[ 'rss$var919' =~ "'$var'" ]]; then echo matches;  fi # trying to string match '$var' fails


    $ if [[ '$var' =~ "'$var'" ]]; then echo matches;  fi # string match still fails as single quotes are omitted on RHS 

    $ if [[ \'$var\' =~ "'$var'" ]]; then echo matches;  fi # this string match works as single quotes are included now on RHS
    matches

Answer 4

正如其他答案中提到的，将正则表达式放入变量中是实现不同版本兼容性的通用方法 巴什 版本。您还可以使用此解决方法来实现相同的目的，同时将正则表达式保留在条件表达式中：

$ number=1
$ if [[ $number =~ $(echo "[0-9]") ]]; then echo matched; fi
matched
$