Let’s make an example. Create 2 folder and put files in it
mkdir dir{1,2}
touch dir1/{1,2,3,4,5,6}.txt
touch dir2/{2,4,5,7,9}.txt
ls -R dir1
dir1:
1.txt 2.txt 3.txt 4.txt 5.txt 6.txt
ls -R dir2
dir2:
2.txt 4.txt 5.txt 7.txt 9.txt
diff -r dir1 dir2
Only in dir1: 1.txt
Only in dir1: 3.txt
Only in dir1: 6.txt
Only in dir2: 7.txt
Only in dir2: 9.txt
http://stackoverflow.com/questions/16787916/difference-between-2-directories-in-linux