如何使用sed命令在模式字符串之前添加字符串? [英] How to use sed command to add a string before a pattern string?

问题描述

我想使用sed修改名为"baz"的文件.

I want to use sed to modify my file named "baz".

当我搜索模式foo时，foo不在行的开头或结尾，我想在foo之前附加小节，我该如何使用sed呢?

When i search a pattern foo , foo is not at the beginning or end of line, i want to append bar before foo, how can i do it using sed?

Input file named baz:
blah_foo_blahblahblah
blah_foo_blahblahblah
blah_foo_blahblahblah
blah_foo_blahblahblah

Output file 
blah_barfoo_blahblahblah
blah_barfoo_blahblahblah
blah_barfoo_blahblahblah
blah_barfoo_blahblahblah

推荐答案

您可以只使用以下内容:

You can just use something like:

sed 's/foo/barfoo/g' baz

(末尾的 g 表示全局，每行而不是仅出现在第一行).

(the g at the end means global, every occurrence on each line rather than just the first).

对于任意 (而不是固定的)模式(例如 foo [0-9] )，可以使用捕获组，如下所示:

For an arbitrary (rather than fixed) pattern such as foo[0-9], you could use capture groups as follows:

pax$ echo 'xyz fooA abc
xyz foo5 abc
xyz fooB abc' | sed 's/\(foo[0-9]\)/bar\1/g'

xyz fooA abc
xyz barfoo5 abc
xyz fooB abc

括号捕获与模式匹配的实际文本， \ 1 使用它代替.

The parentheses capture the actual text that matched the pattern and the \1 uses it in the substitution.

您可以在此模式中使用任意复杂的模式，包括确保仅匹配完整的单词.例如，仅当模式被单词边界立即包围时，才进行更改:

You can use arbitrarily complex patterns with this one, including ensuring you match only complete words. For example, only changing the pattern if it's immediately surrounded by a word boundary:

pax$ echo 'xyz fooA abc
xyz foo5 abc foo77 qqq xfoo4 zzz
xyz fooB abc' | sed 's/\(\bfoo[0-9]\b\)/bar\1/g'

xyz fooA abc
xyz barfoo5 abc foo77 qqq xfoo4 zzz
xyz fooB abc

---

关于捕获组的工作方式，您可以使用括号来存储与模式匹配的文本，以供以后在替换中使用.捕获的标识符基于从左到右读取的(字符，因此是正则表达式(为了简化起见，我省略了 \ 转义字符并对其进行了一些填充):

---

In terms of how the capture groups work, you can use parentheses to store the text that matches a pattern for later use in the replacement. The captured identifiers are based on the ( characters reading from left to right, so the regex (I've left off the \ escape characters and padded it a bit for clarity):

( ( \S* )   ( \S* ) )
^ ^     ^   ^     ^ ^
| |     |   |     | |
| +--2--+   +--3--+ |
+---------1---------+

应用于文本 Pax Diablo 时，将为您提供三组:

when applied to the text Pax Diablo would give you three groups:

\1 = Pax Diablo
\2 = Pax
\3 = Diablo

如下所示:

pax$ echo 'Pax Diablo' | sed 's/\(\(\S*\) \(\S*\)\)/[\1] [\2] [\3]/'
[Pax Diablo] [Pax] [Diablo]

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