Why no output is shown when using grep twice?

Question

Basically I\'m wondering why this doesn\'t output anything:

tail --follow=name file.txt | grep something | grep something_else 

You can ass

Answer 1

works for me on Mac without --follow=name

bash-3.2$ tail delme.txt | grep po
position.bin
position.lrn
bash-3.2$ tail delme.txt | grep po | grep lr
position.lrn