awk打印匹配的行和匹配的行 [英] awk print matching line and line before the matched

问题描述

以下是我尝试使用awk进行的操作.获取与正则表达式匹配的行，以及与之匹配并打印之前的行.我可以得到与正则表达式匹配的行，但不能得到紧接在它之前的行:

Following is what I am trying to do using awk. Get the line that matches the regex and the line immediately before the matched and print. I can get the line that matched the regex but not the line immediately before that:

awk '{if ($0!~/^CGCGGCTGCTGG/) print $0}' 

推荐答案

在这种情况下，您可以使用grep轻松解决它:

In this case you could easily solve it with grep:

grep -B1 foo file

但是，如果您需要使用awk:

However, if you need to to use awk:

awk '/foo/{if (a && a !~ /foo/) print a; print} {a=$0}' file

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