bash命令从文件复制特定行

Question

This copies the last 3 lines of outputs.txt to newfile.txt

tail -n 3 "outputs.txt" | cat >> newfile.txt

but what is the bash command to copy the (last-1)^th and (last-3)^th line of outputs.txt to newfile.txt?

Answer 1

You can use the following

tail -n 4 outputs.txt | awk 'NR ==1 || NR == 3' >> newfile.txt

tail takes the last 4 lines and awk selects the first and third of those, which if I understood correctly are the ones you want.

Note that in your command you don't need cat either, you can just

tail -n3 outputs.txt >> newfile.txt

Answer 2

tac命令可以解决问题。

tac "outputs.txt" |awk 'NR==2 || NR==4' |tac