get all line except n last one
head -n <negative number>we can get the output except n lines
cat a.txt | head -n -1
will gives as the content of a.txt except the last one
Let say we have file 1 2 3 4 5, and with grep we want to only get 1 2 3.
we can achive this with ls and grep
$ ls | grep 4 -B 100000000 | head -n -1
the -B show 100000000 lines before matched line, and the head -n -1 removes the matched