Question

I need to check if a C string is a valid integer.

I tried both

int num=atoi(str);

and

int res=sscanf(str, "%d", &num);

But sending the string "8 -9 10" in both of the lines returned simply 8, without indicating the invalidity of this string.

Can anyone suggest an alternative?

Answer 1

Have a look at strtol(), it can tell you about invalid parts of the string by pointer return.

And beware of enthusiastic example code.. see the man page for comprehensive error-handling.