Re: /dev/random vs. /dev/urandom

Florian Weimer
2005-01-07T19:30:03Z

* Ron Peterson:

> When I compile and run the code below, the string of octal characters
> generated by reading /dev/random contains long strings of zeroes. I was
> under the impression that /dev/random is "more random" than
> /dev/urandom, and will block when it runs out of entropy until it
> gathers more. It's only when RAND_LEN is on the largish side that these
> strings of zeroes appear.

> read( fd, dat, RAND_LEN );

This is the bug. *Always* check the return value of read.

(Try running your program with "strace -e read" for a hint of what's
really going on.)