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

[Florian Weimer <fw@deneb.enyo.de>]

* 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.)