Overwrite last field in last line using awk

Question

I would like to overwrite the last field (2 fields in total) of the last line of a file with the value -9. I am using this command:

awk 'END{$2=-9}1' file.txt > new_file.txt

but it doesn't seem to work (no replacement is done). Why's that? Any ideas?

Thanks!

Answer 1

You'll need to print the previous line, and then you can manipulate the last line in the END block before it has already been printed:

awk 'NR > 1 {print prev} {prev = $0} END {$2=-9; print}'