How do you clear caches on Ubuntu?

At first, I attempted

echo 1 > /proc/sys/vm/drop_caches

Response

-bash: /proc/sys/vm/drop_caches: Permission denied

Adding sudo in front of the command was met with the same result.  What about if I execute the shell as root

sudo sh -c 'echo 1 > /proc/sys/vm/drop_caches'

Success.  Caches cleared.

Different types of clearing cache

Clear PageCache only

sudo sh -c 'echo 1 > /proc/sys/vm/drop_caches'

Clear dentries and inodes

sudo sh -c 'echo 2 > /proc/sys/vm/drop_caches'

Clear pagecache, dentries, and inodes

sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'