Find the files existing in one directory but not in the other [closed]

diff -r dir1 dir2 | grep dir1 | awk '{print $4}' > difference1.txt

Explanation:

• diff -r dir1 dir2 shows which files are only in dir1 and those only in dir2 and also the changes of the files present in both directories if any.

• diff -r dir1 dir2 | grep dir1 shows which files are only in dir1

• awk to print only filename.