c - Sscanf and Sprintf convert string to decimal? -

i need solve following exercise:

"write program acquires first characters of string integer octal , write on string empty, display contents of second string in decimal, using functions sscanf , sprintf. example, if user enters 12 (octal) system must show 10 (decimal)."

after scanf, array seconda ="12325". problem not know how make understand string octal number , how convert decimal sprintf.

this current code:

#include <stdio.h>  int main(void) {     char prima[] = "12325dsdfa";     char secodna[500];      sscanf_s(prima, "%[0123456789]o", secodna, 500); } 

you're mis-using %o, mixing character set format %[] , passing many arguments.

you should use %o, convert unsigned integer octal many characters possible.

then convert decimal string using %u sprintf().

something this:

#include <stdio.h>  int main(void) {     unsigned int x;     if(sscanf("12foo", "%o", &x) == 1)         printf("%u\n", x);     return 0; } 

note above outputs decimal string stdout rather keeping around (i.e. uses printf() instead of sprintf()), that's trivial change. prints "10".