#include <stdlib.h>

       long int random(void);

       void srandom(unsigned int seed);

The random() function uses a nonlinear additive feedback random  number
       generator  employing a default table of size 31 long integers to return
       successive pseudo-random numbers in the range from 0 to RAND_MAX.   The
       period  of  this  random  number generator is very large, approximately
       16 * ((2^31) - 1).

The character special files /dev/random and /dev/urandom (present since
       Linux 1.3.30) provide  an  interface  to  the  kernel's  random  number
       generator.  File /dev/random has major device number 1 and minor device
       number 8.  File /dev/urandom has major device number 1 and minor device
       number 9.

random [-er] [denominator]

random reads lines from the standard input and copies them to the
     standard output with a probability of 1/denominator.  The default value
     for denominator is 2.

     The options are as follows: