Question

I’m using the command grep 3 times on the same line like this

ls -1F ./ | grep / | grep -v 0_*.* | grep -v undesired_result

is there a way to combine them into one command instead of having it to pipe it 3 times?

Answer 1

There’s no way to do both a positive search (grep <something>) and a negative search (grep -v <something>) in one command line, but if your grep supports -E (alternatively, egrep), you could do ls -1F ./ | grep / | grep -E -v '0_*.*|undesired_result' to reduce the sub-process count by one. To go beyond that, you’d have to come up with a specific regular expression that matches either exactly what you want or everything you don’t want.

Actually, I guess that first sentence isn’t entirely true if you have egrep, but building the proper regular expression that correctly includes both the positive and negative parts and covers all possible orderings of the parts might be more frustrating than it’s worth…