You can't sudo echo and redirect from the non-sudo shell like that.

    echo 3 | sudo tee /proc/sys/vm/drop_caches

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

Also fixed your typo in /proc...

▲ throw0101c 2 hours ago | parent | next [-]

Also try:

     sudo sysctl -w vm.drop_caches=3

▲ wpollock an hour ago | parent | prev | next [-]

Or more simply, use

   su -c 'echo 3 > /proc/sys/vm/drop_caches'

	▲	seba_dos1 an hour ago \| parent [-]
		echo 3 \| sudo tee /proc/sys/vm/drop_caches

▲ john_strinlai 2 hours ago | parent | prev [-]

thanks. copy pasting from the github via my phone, and should have taken the extra few mins

	▲	dundarious 32 minutes ago \| parent [-]
		No worries, overall a very useful summary comment.