How to parse strings properly in c

Question

So I have this function :

char *lookUpPageTable(char **array, int VPN)
   {
   if (array[VPN][0] == '1')
      {
      /*char **pageNumber = (char **)malloc(sizeof(char*)* 128);
        for (int i = 0; i < strlen(array); i++)
           {
           pageNumber[i] = array[VPN][i];
           }*/

      return array[VPN]; //this returns the whole number which I dont want
      }
   else
      {
      return "Page Fault";
      }
   }

The array I'm passing in as a parameter holds a list of numbers in the form 1 123456 where the first number is either a 1 or a 0 and the second number is a random number. This function checks the first number at index VPN in the array. If it is a zero, it should return a "Page Fault" string. If it is a 1, then the function should return the number after the 1.

For example, if i called lookUpPageTable(array, index)

The method should see if array[index][0] == '1'

If it does then return the remaining numbers at array[index]

else

return "page fault"

Joseph Myers · Accepted Answer · 2014-05-07 04:10:15Z

1

array[VPN] is the VPN-th element of the array, which happens to be a pointer to the string "1 123456" as you say. If you return array[VPN] + 1, for example, it would be a pointer to the string " 123456".

So you may return array[VPN] + 2, and you will obtain a pointer to the string "123456" as desired.

Note, however, that I am relying on your guarantee that the string's contents are indeed something of the form "1 123456", and I would recommend that your code should also verify that the string really is of that form.

answered May 7, 2014 at 4:10

Joseph Myers

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