07-25-2011
Hi.
Quote:
Originally Posted by
tukuyomi
For the heck of it, using sh and /dev/random ...
There is a characteristic of /dev/random that could become an issue. There may be a limit to how many bits one can pull from /dev/random because it may block. The alternate /dev/urandom is not blocked and is probably as good as /dev/random for many purposes.
For example, I can only get 200-300 numbers from the posted script before /dev/random blocks (Debian 5 -- lenny -- GNU/Linux).
See
/dev/random - Wikipedia, the free encyclopedia for details on this and other aspects ... cheers, drl
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LEARN ABOUT MOJAVE
urandom
RANDOM(4) BSD Kernel Interfaces Manual RANDOM(4)
NAME
random , urandom -- random data source devices.
SYNOPSIS
pseudo-device random
DESCRIPTION
The random device produces uniformly distributed random byte values of potentially high quality.
To obtain random bytes, open /dev/random for reading and read from it.
The same random data is also available from getentropy(2). Using the getentropy(2) system call interface will provide resiliency to file
descriptor exhaustion, chroot, or sandboxing which can make /dev/random unavailable. Additionally, the arc4random(3) API provides a fast
userspace random number generator built on the random data source and is preferred over directly accessing the system's random device.
/dev/urandom is a compatibility nod to Linux. On Linux, /dev/urandom will produce lower quality output if the entropy pool drains, while
/dev/random will prefer to block and wait for additional entropy to be collected. With Yarrow, this choice and distinction is not necessary,
and the two devices behave identically. You may use either.
The random device implements the Yarrow pseudo random number generator algorithm and maintains its entropy pool. The kernel automatically
seeds the algorithm with additional entropy during normal execution.
FILES
/dev/random
/dev/urandom
HISTORY
A random device appeared in the Linux operating system.
Darwin September 6, 2001 Darwin