如何使用grep在*之前和之后找到上下文行？

Question

I need to find out and output 10 lines before pattern and 20 lines after it at once. What am I doing wrong? I don't get the proper result.

grep -B 10 "next" file1.txt | grep -A 20 "next" file1.txt

Answer 1

I need to find out and output 10 lines before pattern and 20 lines after it at once.

You won't get the right result with a pipeline because you won't have the right context lines after piping the output. Instead, put all your context requirements into the same set of command-line arguments. For example:

grep -B 10 -A 20 "next" file1.txt