sed -i ‘s/111/222/g‘ input.txt
awk ‘NR == 2‘ input.txt #output line2
sed -n 2p input.txt #output line2
tail -n2 input.txt #only output the last two lines
tail -n+2 input.txt #from line2 to end
tail -n+2 input.txt|head -n1 #only output line2
原文：https://www.cnblogs.com/xinyueliu/p/12792872.html