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#Give me random numbers to call free
Permission is hereby granted, free of charge, to any person obtaining a copy Calling with a seed will return the same value for the same seed Calling without a seed, the current time will be used as a seed will create an array of 10 random numbers which you can then treat like any array variable: PS C:\> $myrandom = & cscript /nologo "c:\batch\random.js" This has a number of advantages, you can create much larger numbers, it will create a lot of numbers quickly and if you call it passing a seed number then the results become repeatable - you can create exactly the same sequence of random numbers again at a later date. The fastest of these is Alea(), which you can find a copy of below. Johannes Baagøe has published a comparison of better random numbers for javascript. Raymond Chen has a detailed description of Why cmd.exe's %RANDOM% isn’t so random This can be problematic when running a batch file, if the script always takes about the same time to run before calling %RANDOM% then the number returned will always lie within a small predictable range. In the case of the CMD %RANDOM% the seed is based on the clock time when the CMD session started. Random vs Pseudorandom numbersĪ pseudorandom sequence is not truly random but is determined by a small set of initial values (state), the initial seed is often based on the clock time.
If you try, it may look as though a larger range than 32767 will work, but doing this will produce gaps, for example changing 500 in the example above to 65536 will result in a sequence of "random" numbers which only consists of odd numbers. Set /a _rand=(%RANDOM%*(max-min+1)/32768)+minįor example to generate a random number ranging from 1 to OffĮcho Random number %_rand% Limited range of numbers when using %Random% Two commonly given ways to generate a random number in batch: The range of numbers can be made smaller than 32767 with a little arithmetic:ĭividing %RANDOM% by 32768 will produce a random number between 0 and almost 1 (0.999969) notice we are dividing by 327 68 rather than 32767, so we should never get 1 which would give us an uneven distribution of numbers. %RANDOM% generates a random integer from 0 to 32,767 (inclusive) The Windows CMD shell contains a built-in variable called %RANDOM% that can be used to generate random numbers.
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