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Full Discussion: Random Line
Top Forums Shell Programming and Scripting Random Line Post 31875 by Perderabo on Thursday 14th of November 2002 10:47:56 AM
Old 11-14-2002
Suppose that you want to pick a random line froma file that has exactly 100 lines. You can label the lines 0 through 99. Then if you get a random integer, you just take the last two digits as your line number.

Those last 2 digits are the remainder that your get when you divide the random integer by 100. So for example, if the random integer is 10726352; you would have a remainder of 52 after dividing 10726352 by 100. This is expressed as
10726352 % 100 = 52
and % is sometimes called "the remainder function". And sometimes "modulus".

But is was important to divide by 100 since we had 100 lines in our file. When we divide by 100, we have 100 possible remainders, so each line in the file has a chance.

To make this general, don't divide by 100 (or 50) all the time, divide by the count of items.
 

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LEARN ABOUT DEBIAN

unsort

UNSORT(1)						    BSD General Commands Manual 						 UNSORT(1)

NAME

     unsort -- reorder lines in a file in semirandom ways

SYNOPSIS

     unsort [-hvrpncmMsz0l] [--help] [--version] [--random] [--heuristic] [--identity] [--concatenate] [--merge] [--merge-random] [--seed integer]
	    [--zero-terminated] [--null] [--linefeed] [file ...]

DESCRIPTION

     unsort prints the lines in the input files (or standard input) in semi-random order.  Available algorithms are a Mersenne Twister based PRNG
     and a heuristic algorithm that aims to create a subjective even distribution.

   Command line options
     -h, --help
	     Display a concise summary of the available options and argument syntax.

     -v, --version
	     Display version and copyright information.

     -r, --random
	     Use the Mersenne Twister based randomization algorithm.

     -p, --heuristic
	     Use the heuristic "shuffling" algorithm which permutes the lines in such a way that they're spread more or less evenly in the output.
	     This is the default.

     -n, --identity
	     Do not reorder lines in the input. Useful if you just want to merge the files.

     -r, --concatenate
	     Concatenate all input files then apply the shuffling algorithm to the result as a whole.

     -m, --merge
	     Shuffle all input files seperately then merge the result.	Equal-sized files will be merged in the order in which they appear on the
	     command line.

     -M, --merge-random
	     Shuffle all input files seperately then merge the result.	Equal-sized files will be merged in random order.  This is the default.

     -s, --seed integer
	     Use this integer as a seed, instead of random data from the environment.

     -z, --zero-terminated, -0, --null
	     Lines are terminated with a  character.

     -l, --linefeed
	     Lines are terminated with a 
 character.	This is the default.

SEE ALSO

     sort(1)

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