String.indexOf function in C

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

strstr returns a pointer to the found character, so you could use pointer arithmetic: (Note: this code not tested for its ability to compile, it's one step away from pseudocode.)

char * source = "test string";         /* assume source address is */                                        /* 0x10 for example */ char * found = strstr( source, "in" ); /* should return 0x18 */ if (found != NULL)                     /* strstr returns NULL if item not found */ {   int index = found - source;          /* index is 8 */                                        /* source[8] gets you "i" */ } 

Answer 2

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; }