▶ cat things.txt
Zero
One
Two
▶ cat newthings.txt
One
Two
Three
Four
▶ cat newthings.txt | anew things.txt
Three
Four
▶ cat things.txt
Zero
One
Two
Three
Four
#install
sudo git clone https://github.com/tomnomnom/anew.git
cd anew
sudo go build
sudo mv anew /usr/local/bin
anew --help