Use grep to report back only line numbers

Question

I have a file that possibly contains bad formatting (in this case, the occurrence of the pattern \\\\backslash). I would like to use grep to return

Answer 1

If you're open to using AWK:

awk '/textstring/ {print FNR}' textfile

In this case, FNR is the line number. AWK is a great tool when you're looking at grep|cut, or any time you're looking to take grep output and manipulate it.