以下代码
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，它会停止：
number=1
if [[ $number =~ "[0-9]" ]]
then
echo matched
fi
我也试过"\[0-9\]"。我错过了什么？
有趣的是，bash advanced scripting guide 建议这应该有效。
重击版本 3.2.39。
【问题讨论】：
它被更改为between 3.1 and 3.2。猜想高级指南需要更新。
这是对新功能的简要描述 添加到 bash-3.2 的功能 发布 bash-3.1。一如既往， 手册页（doc/bash.1）是地方 寻找完整的描述。
- Bash 中的新功能
剪辑
F。引用字符串参数 [[ 命令的 =~ 运算符现在强制 字符串匹配，与其他模式匹配运算符一样。
遗憾的是，除非您有洞察力将模式存储在变量中并使用它们而不是直接使用正则表达式，否则这将破坏使用脚本的现有报价。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
【讨论】：
if [[ $number =~ ["0-9"] ]]; then echo match; fi
echo或compat31解决方法......
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
使用 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
【讨论】：
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例子
$ 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
【讨论】：
正如其他答案中提到的，将正则表达式放在变量中是实现不同bash 版本兼容性的通用方法。您也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
$
【讨论】：
使用局部变量比使用命令替换的性能稍好。
对于较大的脚本或脚本集合，使用实用程序来防止不需要的局部变量污染代码并减少冗长可能是有意义的。这似乎运作良好：
# Bash's built-in regular expression matching requires the regular expression
# to be unqouted (see https://stackoverflow.com/q/218156), which makes it harder
# to use some special characters, e.g., the dollar sign.
# This wrapper works around the issue by using a local variable, which means the
# quotes are not passed on to the regex engine.
regex_match() {
local string regex
string="${1?}"
regex="${2?}"
# shellcheck disable=SC2046 `regex` is deliberately unquoted, see above.
[[ "${string}" =~ ${regex} ]]
}
用法示例：
if regex_match "${number}" '[0-9]'; then
echo matched
fi
【讨论】：