Pv

Monitor the progress in terms of generated output

Write random data, encode it in base64 and monitor how fast it is being sent to /dev/null

$ cat /dev/urandom | base64 | pv -lbri2 > /dev/null

# pv options:

# -l, lines

# -b, total counter

# -r, show rate

# -i2, refresh every 2 seconds