--brief) option with
diff -r (
diff -qr). From the
info page for GNU
1.6 Summarizing Which Files Differ
When you only want to find out whether files are different, and you
don't care what the differences are, you can use the summary output
format. In this format, instead of showing the differences between
diff' simply reports whether files differ. The--brief'
(`-q') option selects this output format.
This format is especially useful when comparing the contents of two
directories. It is also much faster than doing the normal line by
line comparisons, because `diff' can stop analyzing the files as soon
as it knows that there are any differences.
This will not compare line by line, but rather the file as a whole, which greatly speeds up the processor (what' you're looking for).