Thread: srand(time()) returns segmentation fault

Hey everyone,
Here's another problem I encountered:

when I write this: (This is a beginning of a "guess a number game")

Code:

#include <stdio.h>

main()
{

  int iRandomNum = 0;
  int iResponse = 0;
  srand(time());

  iRandomNum = (rand() % 10) + 1;

...

it returns a segmentation fault. I tested multiple instances, and what I observed is, whenever I define a variable as (rand() % 10) + 1 following srand(time()) it doesn't work and I'm not sure why.

This however works:

Code:

#include <stdio.h>

main()
{

  srand(time());

  printf("\n%d\n", (rand() % 8) + 1);
}

The first code snippet is provided by the book "C programming for the absolute beginner"

Thanks for all the help

time() has to take a parameter. Read the manual! You can pass it NULL:

Code:

srand(time(NULL));

Calling it without the parameter is equal to calling it with garbage. So your program crashes.

Thanks brewbuck for the rapid help.

It works!

wait but actually I have another question, how come it works without a NULL in this code?
Thanks again for the help,

Code:

#include <stdio.h>

main()
{

  int iRandomNum = 0;
  srand(time());

  iRandomNum = (rand() % 4) + 1;

  printf("\nFortune Cookie-Chapter 3\n");

  switch (iRandomNum) {

  case 1:
    printf("\nYou will meet a new friend today.\n");
    break;
  case 2:
    printf("\nYou will enjoy a long and happy life.\n");
    break;
  case 3:
    printf("\nOpportunity knocks softly. Can you hear it?\n");
    break;
  case 4:
    printf("\nYou'll be financially rewarded for your good deeds.\n");
    break;
  } // end switch
} // end main

Originally Posted by withoutn

wait but actually I have another question, how come it works without a NULL in this code?

Random freaking chance. When you play Russian Roulette, 5 times out of 6 you survive.

Hey, it's me again. Sorry for bugging you with all these questions, but I just wrote this, and I get a segmentation fault again.

Code:

#include <stdio.h>

main()
{

  int intRandomNum = 0;
  int intResponse = 0;
  srand(time(NULL));

  intRandomNum = (rand() % 10) + 1;

  printf("\n Guess a number between 1 and 10: ");
  scanf("%d", intResponse);

  if (intRandomNum == intResponse)
    printf("\n You got it!\n\n");
  else
    printf("\n Wrong! The correct number is: %d\n\n", intRandomNum);
}

Not using scanf() correctly. You need to pass it a pointer to a location to store the result, not the variable itself. Change is made in red below:

Code:

#include <stdio.h>

main()
{

  int intRandomNum = 0;
  int intResponse = 0;
  srand(time(NULL));

  intRandomNum = (rand() % 10) + 1;

  printf("\n Guess a number between 1 and 10: ");
  scanf("%d", &intResponse);

  if (intRandomNum == intResponse)
    printf("\n You got it!\n\n");
  else
    printf("\n Wrong! The correct number is: %d\n\n", intRandomNum);
}

Oh yes, now it's fine. Thanks for aaaall the help. Sorry for taking up your time :-)

it works because you don't include time.h. If you did, it would give you an error.