Question

/* strchr example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char str[] = "This is a sample string";
  char * pch;
  printf ("Looking for the 's' character in \"%s\"...\n",str);
  pch=strchr(str,'s');
  while (pch!=NULL)
  {
    printf ("found at %d\n",pch-str+1);
    pch=strchr(pch+1,'s');
  }
  return 0;
}

How would I index the str so that I would replace every ‘s’ with ‘r’.

Thanks.

Answer 1

You don’t need to index the string. You have a pointer to the character you want to change, so assign via the pointer:

*pch = 'r';

In general, though, you index using []:

ptrdiff_t idx = pch - str;
assert(str[idx] == 's');