Basically I want to take as input text from a file, remove a line from that file, and send the output back to the same file. Something along these lines if that makes it any
try this simple one
grep -v 'seg[0-9]\{1,\}\.[0-9]\{1\}' file_name | tee file_name
Your file will not be blank this time :) and your output is also printed to your terminal.