People often say "you can refactor that line and save a useless invocation of cat" cat /var/log/file.log Output too long, so Press Up, |grep -e useful -e l

People often say "you can refactor that line and save a useless invocation of cat" cat /var/log/file.log Output too long, so Press Up, |grep -e useful -e lines cat /var/log/file.log|grep -e useful -e lines OK, that looks fine, but I want to tail it Press Up, Home, deldeldel, tail -f (other terminal modes are available) tail -f /var/log/file.log|grep -e useful -e lines Exact same command no matter what grep -e you have. You separate the filtering logic from the accessing logic. You can work on one side without worrying about the other. Want to change from cat to bzcat, or tail, or tac, or nc? No problem. Want to add a pre-filter (say strip snmpd errors before you add -n to number your matches in grep), it all stays the same. Now imagine this without "useless" cat less /var/log/file.log Press Up, Home, deldeldeldelgrep -e useful -e lines grep -e useful -e lines /var/log/file.log Then either Press up, home, del(n times), tail, end, | grep -e useful -e lines Or Press up, up, |grep -e useful -e lines, home, deldeldel, tail -f Cognative break, extra typing, potentially having to look at what you're typing too rather than muscle memory, all because someone says "cat is useless". My computer isn't from 1965, I don't need to justify every process I run.