The command-line Linux program diff allows you to check for differences between files and folders.
Compare Two Folders
The following command will make diff compare two folders:
$ diff Folder1 Folder2
Compare Two Files
The syntax is pretty much the same as if you were to compare two folders. The following command will make diff compare two files:
$ diff file1 file2
Quietning The Output
-q option tells diff to print less output. When comparing folders, this will stop diff from printing the changed content of a file it recognises in both folders, and instead will just tell you that the file has been changed.
diff -q Folder1 Folder2