Grep表示文本文件中交替模式A和模式B的行

Question

可以使用grep来搜索交替模式，即第一个模式A，然后是模式B，然后是模式A，然后是模式B等。

我有一个这样的txt文件：

some lines
some line containing pattern B
some lines
some line containing pattern A
some line containing pattern B
some line containing pattern B
some line containing pattern A
some line containing pattern A
some line containing pattern B

我喜欢用交替模式A和模式B来画线。像这样：

some lines
some line containing pattern B  <- Don't take this (no A before)
some lines
some line containing pattern A  <- Take
some line containing pattern B  <- Take
some line containing pattern B  <- Don't take this (no A before)
some line containing pattern A  <- Take
some line containing pattern A  <- Don't take this (no B before)
some line containing pattern B  <- Take

所以我的最终结果是：

some line containing pattern A
some line containing pattern B
some line containing pattern A
some line containing pattern B

Answer 1

这可以做你想要的。

 awk '{m=a>b?a:b;} /pattern A/{a=NR} /pattern B/{b=NR}(m&&m==a&&a<b)||(m&&m==b&&b<a)' awkx

<强>样本

lo@ubuntu:~$ awk '{m=a>b?a:b;} /pattern A/{a=NR} /pattern B/{b=NR}(m&&m==a&&a<b)||(m&&m==b&&b<a)' awkx
some line containing pattern A
some line containing pattern B
some line containing pattern A
some line containing pattern B