bash shell 脚本中的“=~”运算符有什么作用？
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What does the "=~" operator do in shell scripts?
提问by penartur
It seems that it is sort of comparison operator, but what exactly it does in e.g. the following code (taken from https://github.com/lvv/git-prompt/blob/master/git-prompt.sh#L154)?
似乎它是一种比较运算符，但是它在例如以下代码（取自https://github.com/lvv/git-prompt/blob/master/git-prompt.sh#L154）中究竟做了什么？
if [[ $LC_CTYPE =~ "UTF" && $TERM != "linux" ]]; then
elipses_marker="…"
else
elipses_marker="..."
fi
I'm currently trying to make git-promptto work under MinGW, and the shell supplied with MinGW doesn't seem to support this operator:
我目前正在尝试git-prompt在 MinGW 下工作，MinGW 提供的 shell 似乎不支持这个操作符：
conditional binary operator expected
syntax error near `=~'
` if [[ $LC_CTYPE =~ "UTF" && $TERM != "linux" ]]; then'
In this specific case I can just replace the entire block with elipses_marker="…"(as I know my terminal supports unicode), but what exactly this =~does?
在这种特定情况下，我可以将整个块替换为elipses_marker="…"（因为我知道我的终端支持 unicode），但这究竟是=~做什么的？
采纳答案by MattBianco
It's a bash-only addition to the built-in [[command, performing regexp matching. Since it doesn't have to be an exact match of the full string, the symbol is waved, to indicate an "inexact" match.
它是对内置[[命令的仅 bash 补充，用于执行正则表达式匹配。由于它不必是完整字符串的精确匹配，因此会挥动符号，以表示“不精确”匹配。
In this case, if $LC_CTYPECONTAINSthe string "UTF".
在这种情况下，如果$LC_CTYPECONTAINS字符串“UTF”。
More portable version:
更便携的版本：
if test `echo $LC_CTYPE | grep -c UTF` -ne 0 -a "$TERM" != "linux"
then
...
else
...
fi
回答by Micha? Górny
It's a regular expression matching. I guess your bash version doesn't support that yet.
这是一个正则表达式匹配。我猜你的 bash 版本还不支持。
In this particular case, I'd suggest replacing it with simpler (and faster) pattern matching:
在这种特殊情况下，我建议用更简单（更快）的模式匹配替换它：
[[ $LC_CTYPE == *UTF* && $TERM != "linux" ]]
(note that *must not be quoted here)
（注意*这里不能引用）
回答by alex
Like Ruby, it matches where the RHS operand is a regular expression.
与 Ruby 一样，它匹配 RHS 操作数是正则表达式的地方。
回答by Rozuur
It matches regular expressions
它匹配正则表达式
Refer to following example from http://tldp.org/LDP/abs/html/bashver3.html#REGEXMATCHREF
请参阅http://tldp.org/LDP/abs/html/bashver3.html#REGEXMATCHREF 中的以下示例
#!/bin/bash
input=
if [[ "$input" =~ "[0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]" ]]
# ^ NOTE: Quoting not necessary, as of version 3.2 of Bash.
# NNN-NN-NNNN (where each N is a digit).
then
echo "Social Security number."
# Process SSN.
else
echo "Not a Social Security number!"
# Or, ask for corrected input.
fi
