The strpos function searches string for the first occurrence of c. The null character terminating string is included in the search.

The strpos function returns the index of the character matching c in string or a value of -1 if no matching character was found. The index of the first character in string is 0.

strchr, strcspn, strpbrk, strrchr, strrpbrk, strrpos, strspn

#include <string.h>
#include <stdio.h> /* for printf */

void tst_strpos (void) {
  char text [] = "Search this string for blanks";
  int i;

  i = strpos (text, ' ');

  if (i == -1)
    printf ("No spaces found in %s\n", text);
  else
    printf ("Found a space at offset %d\n", i);
}