how can I diff two sections of the same file?

Question

I have a source file with two similar yet subtly different sections. I\'d like to merge the two sections into one subroutine with a parameter that handles the subtle difference

Answer 1

If you can describe the start and end of the sections to compore with a regex you can use the following:

sh -c 't=`mktemp`; cat "$0" | grep -e "$2" -A10000 | grep -e "$3" -B 10000 > $t; cat "$1" | grep -e "$2" -A10000 | grep -e "$3" -B 10000 | diff -u $t - ; rm $t' firstfile secondfile "section start" "section end"

As an alternative you if you want to describe the section by line number you can do:

sh -c 't=`mktemp`; cat "$0" | head -$3 |tail +$2 > $t; cat "$1" | head -$5 | tail +$4 | diff -u $t - ; rm $t' first second 4 10 2 8

4 10 2 8 is the start and end line number for the section to consider from the first file and the second file.

You can either save the snippets a shell scripts or as aliases.