仅解析具有多个匹配项的行中的第一个正则表达式匹配项 [英] Parsing only first regex match in a line with several matches

问题描述

是否可以有一个仅从该行a1bcdea1ABCa1DEFa1解析a1bcdea1的正则表达式?

Is it possible to have a regex that parses only a1bcdea1 from this line a1bcdea1ABCa1DEFa1 ?

此grep命令不起作用:

This grep command does not work:

$ cat txtfile
a1bcdea1ABCa1DEFa1
$ grep -oE "[A-Z,a-z]1.*?[A-Z,a-z]1" txtfile
a1bcdea1ABCa1DEFa1

我希望grep的输出仅为a1bcdea1.

I want the output of grep to be only a1bcdea1.

很明显，我可以在上面的行中使用grep -o"a1bcdea1"，但是要考虑一个行是否有几千行，并且目标是每行都匹配第一个[A-Z,a-z]1.*?[A-Z,a-z]1.

It is obvious that I can just use grep -o "a1bcdea1" for the above line, but consider if one has several thousands of lines and the goal is to match FIRST [A-Z,a-z]1.*?[A-Z,a-z]1 for each single line.

推荐答案

如何使用 ^开始锚点并限制使用的字符集:

How about using a ^ start anchor and restricting character set used:

grep -o '^[A-Za-z]1[A-Za-z]*1'

>或如果您希望两者之间有更多的数字或其他字符，请使用与此

If you expect more digits or other characters in between, go with this

grep -oP '^[A-Za-z]1.*?[A-Za-z]1'

惰性匹配要求与此

The lazy matching requires perl compatible mode. For not at line start, go with this

grep -oP '^.*?\K[A-Za-z]1.*?[A-Za-z]1'

\K重置报告的匹配开始也是PCRE的功能.

\K resets beginning of the reported match and is a PCRE feature as well.

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