05-16-2010
Generate random number
I saw this formula to generate random number between two specified values in shell script.the following.
$(((RANDOM%(max-min+divisibleBy))/divisibleBy*divisibleBy+min))
Give a example in book.
Generate random number between 6 and 30.like this.
$(((RANDOM%30/3+1)*3))
But I have a question , how to get a divisibleBy number is ok.
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MT_RAND(3) 1 MT_RAND(3)
mt_rand - Generate a better random value
SYNOPSIS
int mt_rand (void )
DESCRIPTION
int mt_rand (int $min, int $max)
Many random number generators of older libcs have dubious or unknown characteristics and are slow. By default, PHP uses the libc random
number generator with the rand(3) function. The mt_rand(3) function is a drop-in replacement for this. It uses a random number generator
with known characteristics using the Mersenne Twister, which will produce random numbers four times faster than what the average libc
rand() provides.
If called without the optional $min, $max arguments mt_rand(3) returns a pseudo-random value between 0 and mt_getrandmax(3). If you want a
random number between 5 and 15 (inclusive), for example, use mt_rand(5, 15).
Caution
This function does not generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a
cryptographically secure value, consider using random_int(3), random_bytes(3), or openssl_random_pseudo_bytes(3) instead.
PARAMETERS
o $min
- Optional lowest value to be returned (default: 0)
o $max
- Optional highest value to be returned (default: mt_getrandmax(3))
RETURN VALUES
A random integer value between $min (or 0) and $max (or mt_getrandmax(3), inclusive), or FALSE if $max is less than $min.
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.3.4 | |
| | |
| | Issues an E_WARNING and returns FALSE if $max < |
| | $min. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
mt_rand(3) example
<?php
echo mt_rand() . "
";
echo mt_rand() . "
";
echo mt_rand(5, 15);
?>
The above example will output something similar to:
1604716014
1478613278
6
NOTES
Caution
The distribution of mt_rand(3) return values is biased towards even numbers on 64-bit builds of PHP when $max is beyond 2^32. This
is because if $max is greater than the value returned by mt_getrandmax(3), the output of the random number generator must be scaled
up.
SEE ALSO
mt_srand(3), mt_getrandmax(3), random_int(3), random_bytes(3), openssl_random_pseudo_bytes(3), rand(3).
PHP Documentation Group MT_RAND(3)