從man bash
,/RANDOM
RANDOM Each time this parameter is referenced, a random integer between 0 and 32767 is generated. The sequence of random numbers may be initialized by assigning a value to RANDOM. If RANDOM is unset, it loses its
special properties, even if it is subsequently reset.
說明書並沒有說這是如何實現的。
否則從sources:variables.c顯示,隨機連接的功能get_random
INIT_DYNAMIC_VAR ("RANDOM", (char *)NULL, get_random, assign_random);
這就要求get_random_number
,seedrand
和brand
/* A linear congruential random number generator based on the example
one in the ANSI C standard. This one isn't very good, but a more
complicated one is overkill. */
/* Returns a pseudo-random number between 0 and 32767. */
static int
brand()
{
/* From "Random number generators: good ones are hard to find",
Park and Miller, Communications of the ACM, vol. 31, no. 10,
October 1988, p. 1195. filtered through FreeBSD */
long h, l;
/* Can't seed with 0. */
if (rseed == 0)
rseed = 123459876;
h = rseed/127773;
l = rseed % 127773;
rseed = 16807 * l - 2836 * h;
#if 0
if (rseed < 0)
rseed += 0x7fffffff;
#endif
return ((unsigned int)(rseed & 32767)); /* was % 32768 */
}