I know I can use -A, -B and -C to show surrounding lines but all of them also show the matching line. What I'm trying to make here is so, in this example file:
foo
bar
I'd be doing something like grep <option> "bar" file and my output should be
foo
Side note: I know the way of doing it with another grep or using sed but I would like to do it just by using one time grep
It's quite a job for sed:
$ printf 'foo\nbar\n' | sed -n '$!N;/\nbar$/P;D'
foo
$!N -> If not last line, append next line to the pattern space. So If you are in line 1, your pattern space will look like line 1\nline2. Then /\nbar$/ will match if line 2 is bar. If yes, Print line 1, then Delete the rest of pattern space \nline 2.
– cuonglm
Oct 02 '20 at 08:10
yet another solution
grep -B 1 "bar" test | head -n 1
it has the advantage that you don't need any additional regexp or matching test, it is therefore more efficient but this won't work for multiple match
You could do another grep which ignores "bar":
grep -B 1 "bar" test.txt | grep -v "bar"
bar? what should it return ? – PinkFloyd May 30 '16 at 08:22