Seeds the pseudo-random number generator used byrand() with the valueseed.

Ifrand() is used before any calls tosrand(),rand() behaves as if it was seeded withsrand(1).

Each timerand() is seeded with the sameseed, it must produce the same sequence of values.

srand() is not guaranteed to be thread-safe.

[edit]Parameters

[edit]Return value

(none)

[edit]Notes

Generally speaking, the pseudo-random number generator should only be seeded once, before any calls torand(), and the start of the program.It should not be repeatedly seeded, or reseeded every time you wish to generate a new batch of pseudo-random numbers.

Standard practice is to use the result of a call totime(0) as the seed.However,time() returns atime_t value, andtime_t is not guaranteed to be an integral type.In practice, though, every major implementation definestime_t to be an integral type, and this is also what POSIX requires.

[edit]Example

#include <stdio.h>#include <stdlib.h>#include <time.h> int main(void){    srand(time(NULL));//use current time as seed for random generatorint random_variable=rand();printf("Random value on [0,%d]: %d\n",RAND_MAX, random_variable);}

Random value on [0 2147483647]: 1373858591

[edit]References

[edit]See also

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