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Top Forums Shell Programming and Scripting choose random text between constant string.. using awk? Post 302394991 by drl on Sunday 14th of February 2010 07:15:27 AM
Old 02-14-2010
Hi.
Quote:
Originally Posted by ironmask2004
but you need to know how muche recoreds you have insaide the fill to generate a random number betwwen 1 and NUM Of Rec !!!
If one is willing to devote the time and effort, the reservoir sampling method allows one to extract a random sample in a single pass through a file. A brief explanation along with a python and perl code can be found at Program-o-Babble: Reservoir Sampling Algorithm in Python and Perl among many other places.

Best wishes ... cheers, drl
 

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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
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