How to execute the abc command and redirect the output of the error stream to the file error.txt, as well as display the error stream on the screen without empty lines?

Question

bash

The output of errors to a file is understandable:
abc | abc 2>error.txt
But I can’t figure out how to make the output in the terminal without empty lines.
Tried
sed '${/^$/d;}'and grep -v '^$'
doesn't work.
Please help, it is advisable to poke where to read (except for man in bourgeois: ()

Answer 1

Output without blank lines
abc | sed '/^$/d'

Answer 2

echo -e "hello\nworld\n\n and me" 2>/dev/null | grep -v '^$'

Your solution should work, just put the redirects in the right order