Another Random Post

Hal Pomeranz suggests this one-liner

head /dev/urandom | tr -dc 0-9 | sed -r 's/(.{8})/\1\n/g'

for generating big batches of random numbers. It's a winner: reasonable performance and easy-to-type. Timing information follows:

#!/bin/bash

echo == Shell arithmetic

(( R = 2**15-1, T = 10**8-1, C = T/R ))

readonly R T C

time for i in {0..10000}

do

printf "%8.8u\n" $(( RANDOM*C + ( RANDOM%C ) ))

done > /dev/null

echo; echo == Pipeline

time head -10000 /dev/urandom | tr -dc 0-9 | sed -r 's/(.{8})/\1\n/g' | head -10000 > /dev/null

Here's the numbers:

== Shell arithmetic

real 0m0.262s

user 0m0.256s

sys 0m0.004s

== Pipeline

real 0m0.421s

user 0m0.028s

sys 0m0.392s

Okay, the pipe's a little slower, but it's the same order of magnitude, and way easier to type.