Answer by schrodingerscatcuriosity for Show all lines before a match

Here's a solution with sed, given the content of file.txt:

barbazmoofooloozoo

command including pattern

tac file.txt | sed -n '/foo/,$p' | tac

output

barbazmoofoo

excluding pattern

tac file.txt | sed -n -e '/foo/,$p' | tac | sed -n '/foo/!p'barbazmoo