不区分大小写的搜索并替换为 sed [英] Case-insensitive search and replace with sed

问题描述

我正在尝试使用 SED 从日志文件中提取文本.我可以毫不费力地进行搜索和替换:

I'm trying to use SED to extract text from a log file. I can do a search-and-replace without too much trouble:

sed 's/foo/bar/' mylog.txt

但是，我想让搜索不区分大小写.从我用谷歌搜索的内容来看，似乎将 i 附加到命令的末尾应该可以:

However, I want to make the search case-insensitive. From what I've googled, it looks like appending i to the end of the command should work:

sed 's/foo/bar/i' mylog.txt

然而，这给了我一个错误信息:

However, this gives me an error message:

sed: 1: "s/foo/bar/i": bad flag in substitute command: 'i'

这里出了什么问题，我该如何解决?

What's going wrong here, and how do I fix it?

推荐答案

更新:从ma​​cOS Big Sur (11.0)开始，sed 现在 does 支持 I 标志用于不区分大小写的匹配，所以问题中的命令现在应该可以工作(BSD sed 不报告其版本，但您可以查看 man 页面底部的日期，该日期应该是 March 27, 2017 或更近期)；一个简单的例子:

Update: Starting with macOS Big Sur (11.0), sed now does support the I flag for case-insensitive matching, so the command in the question should now work (BSD sed doesn't reporting its version, but you can go by the date at the bottom of the man page, which should be March 27, 2017 or more recent); a simple example:

# BSD sed on macOS Big Sur and above (and GNU sed, the default on Linux)
$ sed 's/ö/@/I' <<<'FÖO'
F@O   # `I` matched the uppercase Ö correctly against its lowercase counterpart

^{注意:I(大写)是标志的文档形式，但 i 也能工作.}

^{Note: I (uppercase) is the documented form of the flag, but i works as well.}

同样，从 ma​​cOS Big Sur (11.0) awk 现在是区域设置感知(awk --version 应该报告 20200816 或更新的):

Similarly, starting with macOS Big Sur (11.0) awk now is locale-aware (awk --version should report 20200816 or more recent):

# BSD awk on macOS Big Sur and above (and GNU awk, the default on Linux)
$ awk 'tolower($0)' <<<'FÖO'
föo  # non-ASCII character Ö was properly lowercased

---

以下适用于 ma​​cOS 直到 Catalina (10.15):

---

The following applies to macOS up to Catalina (10.15):

要明确:在 macOS 上，sed - 这是 BSD 实现 - 不支持不区分大小写的匹配 - 很难相信， 但是是真的.以前接受的答案，它本身显示了一个 GNU sed 命令，由于评论中提到的基于 perl 的解决方案而获得该状态.

To be clear: On macOS, sed - which is the BSD implementation - does NOT support case-insensitive matching - hard to believe, but true. The formerly accepted answer, which itself shows a GNU sed command, gained that status because of the perl-based solution mentioned in the comments.

要使 Perl 解决方案也适用于外来字符，请通过 UTF-8，使用以下内容:

To make that Perl solution work with foreign characters as well, via UTF-8, use something like:

perl -C -Mutf8 -pe 's/öœ/oo/i' <<< "FÖŒ" # -> "Foo"

• -C 为流和文件开启 UTF-8 支持，假设当前语言环境是基于 UTF-8 的.
• -Mutf8 告诉 Perl 将源代码解释为 UTF-8(在这种情况下，字符串传递给 -pe) -这是更详细的 -e 'use utf8;' 的较短等价物.^{谢谢，马克·里德}
• -C turns on UTF-8 support for streams and files, assuming the current locale is UTF-8-based.
• -Mutf8 tells Perl to interpret the source code as UTF-8 (in this case, the string passed to -pe) - this is the shorter equivalent of the more verbose -e 'use utf8;'.^{Thanks, Mark Reed}

(请注意，使用 awk 也不是一种选择，因为 awk 在 macOS 上(即 BWK awk 和 BSD awk) 似乎完全不知道语言环境 - 它的 tolower() 和 toupper() 函数忽略外来字符(和 sub()/gsub() 开始时没有不区分大小写的标志.)

(Note that using awk is not an option either, as awk on macOS (i.e., BWK awk and BSD awk) appears to be completely unaware of locales altogether - its tolower() and toupper() functions ignore foreign characters (and sub() / gsub() don't have case-insensitivity flags to begin with).)

关于 sed 和 awk 与 POSIX 标准的关系的注释:

A note on the relationship of sed and awk to the POSIX standard:

BSD sed 和 awk 将它们的功能主要限制在 POSIX sed 和POSIX awk 规范要求，而他们的GNU 对应版本实现了更多扩展.

BSD sed and awk limit their functionality mostly to what the POSIX sed and POSIX awk specs mandate, whereas their GNU counterparts implement many more extensions.

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