diff -rq folder_1 folder_2
Here is what the above code is Doing:
1. The -r option tells diff to recursively compare any subdirectories found.
2. The -q option tells diff to be “quiet” and not to output any of the files that are the same.
3. The first folder_1 is the first directory to compare.
4. The second folder_2 is the second directory to compare.