Answer by Meaulnes for deleting directory with large amount of files with rsync -a delete

according to linuxnote.net's webarchive is rsync -aP –delete empty/ ./dir the fastest way to delete large directories, about three times faster as with rm -rfv ./dir or with find b/ -type f -delete

since it can take a while, a verbose output with -P is convenient or you gaze at an empty prompt line for ever...

and in order to avoid endless scrolling, I redirected the STDOUT to awk to display the output on a single line (with a line counter) like this:

rsync -aP --delete ./emptyDir/ ./dir/ | awk ' { printf ( "\r #%4d: %-200s", NR, $0 ) } '

for skipping the Permission denied lines, use sudo:

sudo rsync -aP --delete ./emptyDir/ ./dir/ | awk'{printf("\r #%4d: %-200s",NR,$0)}'

explanation: awk because printf alone doesn't catch STDOUT, \r to set the cursor at the begin of the output line, NR for a line# counter and %4d right-pads the line# and %-200s for an output string of 200 chars right padded that overwrites the previous line (200 if terminal window has at least this width)