rand(3)                                                         rand(3)

  rand()

  NAME

    rand(), rand_r(), srand() - system random number generator

  SYNOPSIS

    #include 

    void srand (unsigned seed)
    int rand (void)
    int rand_r (unsigned *seed)

  DESCRIPTION

    The rand(3) function computes a sequence of pseudo-random integers in the
    range of 0 to {RAND_MAX} (as defined in the header file ).

    The srand(3) function sets its argument as the seed for a new sequence of
    pseudo-random numbers to be returned by rand(3). These sequences are
    repeatable by calling srand(3) with the same seed value.

    The reentrant rand_r(3) function computes a sequence of pseudo-random
    integers in the range of 0 to {RAND_MAX}. If rand_r(3) is called with the
    same initial value for the object identified by the seed argument and that
    object is not modified between successive returns and calls to rand_r(3),
    the same sequence is generated.

    If no seed value is provided, the functions are automatically seeded with
    a value of 1.

    To seed the random number generator with the time (a popular source), you
    can use:

    srand((unsigned int)time(NULL));

  SEE ALSO

    random(3)

  USAGE NOTES

    The following functions are thread safe: rand_r, srand. The rand function
    is not thread safe.

    None of these functions are async-signal safe.