Using memory adress from pointer to print character array (string) C

Question

char mening[] = "tjena pa dig hog";

This string contains 16 characters. I am then using a function adresss() to find the memory address of a random character in that array. The function adresss() returns a pointer containing the address. The address is at this moment 0x7ffeefbff5f9. I now need to know what positions that address is pointing to, example is it pointing to the "t" at position 0 in the array, or maybe it is pointing to "d" at position 9. How do I do this?

Edit:

char* adresss(char mening[]){

   //Lots of code going on here

   return &mening[i];
}

int main(void){
   char mening[] = "tjena pa dig hog";
   char* ptr;
   ptr = adresss(mening);

   printf("%p\n", ptr);

That is basically how I get the memory adress. I want to know what "i" was, inside the main function only knowing the memory adress.

The adresss() function is returning like this: return &mening[i]; that will give the adress of position i in mening[] I want to find i again using only the memory adress — J. Doe
– J. Doe, Commented Feb 19, 2018 at 16:21
While the number of elements of the array mening is 16, remember that the last one (with index 15) is the string terminator. — Some programmer dude
– Some programmer dude, Commented Feb 19, 2018 at 16:25
@Someprogrammerdude.: The array has size 17 and index 15 is g. — user2736738
– user2736738, Commented Feb 19, 2018 at 16:37

Some programmer dude · Accepted Answer · 2018-02-19 16:21:07Z

1

If you have two pointers, both pointing to the same array (or to one beyond the end of the array), then you can subtract them from each other.

For example:

char mening[] = "tjena pa dig hog";
char *pointer_to_mening = &mening[10];  // Pointer to the eleventh character

// Should print 10 (which is the index of the eleventh character)
printf("The distance is %zu\n", pointer_to_mening - mening);

answered Feb 19, 2018 at 16:21

Some programmer dude

411k36 gold badges420 silver badges655 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

J. Doe Over a year ago

What does %zu mean?

Some programmer dude Over a year ago

@J.Doe "%u" is to print an unsigned int. The z modifier is for size_t arguments. That means "%zu" prints a size_t argument as an unsigned integer. See e.g. this printf (and family) reference for more details.

Collectives™ on Stack Overflow

Using memory adress from pointer to print character array (string) C

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related