Adding strings to 2D array in C

Question

I'm trying to write a program that looks for the first empty space in a 2D array and adds a custom string to that space. I have tried some things that i found on the internet but none seem to work or match my specific scenario. This is it:

#include <stdio.h>
#include <string.h>

int tags[10] = {1,2,3,4,5};
char owners[10][10] = {"per1", "per2", "per3", "per4", "per5"};
int tagAdd;
char ownerAdd;
int i;
int addBool;
int j;
int len;

int main()
{
   printf("Enter the tag ID you want to add: ");
   scanf("%d", &tagAdd);
   printf("Enter the tag owners name: ");
   scanf("%d", &ownerAdd);
   len = strlen(ownerAdd);

   while (i<10)
   {
       if (tags[i] == 0)
       {
           tags[i] = tagAdd;
           owners[i][len] = ownerAdd; //This is the part I can't figure out
           addBool = 1;
       }
       if (addBool == 1)
       {
           break;
       }
       i++;
   }

   i = 0;
   addBool = 0;
   len = 0;

   while (i<10)
   {
       printf("tag[%d]", tags[i]);
       len = strlen(owners[i]);
       printf(" is owned by ");
       while (j < len)
           {
               printf("%c", owners[i][j]);
               j++;
           }
       printf("\n\r");
       i++;
       j = 0;
   }

}

"first empty space in a 2D" is a bit unclear. A 2D array can not have any empty space. In this case, the 2D char owners[10][10] consists of 10*10 or 100 elements (char). Looks like this is more about char owners[10][10] as 10 strings and code is looking for the first string that begins with a null character. — chux
– chux, Commented Feb 9, 2018 at 20:42

Pablo · Accepted Answer · 2018-02-09 19:56:21Z

0

You cannot do this:

char ownerAdd;

scanf("%d", &ownerAdd);
len = strlen(ownerAdd);

You are passing the incorrect types. ownerAdd is a single char, scanf expects with %d a pointer to int, you are passing a pointer to char and if scanf converts the value, it will overflow. And strlen expects a char* which points to a valid string (0-terminated). You are doing all this wrong.

This would be correct:

char ownerAdd[100];
scanf("%99s", ownerAdd);
len = strlen(ownerAdd);

And for replacing a value:

owners[i][len] = ownerAdd; //This is the part I can't figure out

is also wrong, because owners[i] is a char[10], you have to do:

strncpy(owners[i], ownerAdd, sizeof owners[i]);
owners[i][sizeof(owners[i]) - 1] = 0;

to copy the string.

The next error is that you don't initialize i and do (the first loop)

while (i<10)
{
    ...
}

this is going to fail. Same thing with j, it is uninitialized.

answered Feb 9, 2018 at 19:56

Pablo

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1 Comment

Wardk Over a year ago

There defenitely were alot of flaws in my code, thanks alot for helping me out here!

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