Percentile is a unix tool to calculate percentile while on the command line. It accepts a set of float's separated by new lines piped into the tool. It then calculates a set of percentiles that are given as command line arguments. If no arguments are given it will calculate the median and 95th percentile.
--> seq 1 10000| ./percentile 10 15 20.5 50 99 99.999
Pctl 10.000: 1000.00
Pctl 15.000: 1500.00
Pctl 20.500: 2050.00
Pctl 50.000: 5000.00
Pctl 99.000: 9900.00
Pctl 99.999: 10000.00