Grep only a part of a text file

Question

How can I apply the following command to only a part of a text file? For example from the beginning to the line 5000.

grep "^  A : 11  B : 10" filename | wc -l

I cannot use head and then apply the above command since the text file is huge.

Answer 1

您可以尝试使用sed命令，从这个问题到管道，再到grep，我相信它对于大型文件会更好。

sed -n 1,5000p file | grep ...

Answer 2

You can try combination of -n (prefixing each line of output with line number) and -m (limiting number of matching lines). Something like this:

grep -n -m 5000 pattern file.txt | grep -B 5000 "^5000:" | wc -l

First grep search for pattern, add line numbers and limit output to first 5000 matching lines (worst case scenario: all lines from range match pattern). Second grep match line number 5000, and print all lines before this line.

I don't know if it is more efficient solution