random number

random 0-9, 其實用 pid / time 其中一個做 seed 都 ok, 不過用 time - pid 都唔算係好花 resource 啊.

#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <time.h>

main()
{
        int j;
        pid_t mypid;
        time_t now;

        mypid = getpid();
        now = time(NULL);

        printf("pid = %d\n",mypid);
        printf("time = %d\n",now);

        srand((int)time - mypid);
        j=(int) (10.0*rand()/(RAND_MAX));
        printf("j = %d\n",j);

        j=(int) (10.0*rand()/(RAND_MAX));
        printf("j = %d\n",j);
}