Question

Is there a C library function that will return the index of a character in a string?

So far, all I’ve found are functions like strstr that will return the found char *, not it’s location in the original string.

Answer 1

I think that

size_t strcspn ( const char * str1, const char * str2 );

is what you want. Here is an example pulled from here:

/* strcspn example */ #include <stdio.h> #include <string.h>  int main () {   char str[] = 'fcba73';   char keys[] = '1234567890';   int i;   i = strcspn (str,keys);   printf ('The first number in str is at position %d.\n',i+1);   return 0; }