将字符串中的数字转换为 integer 时出现 atoi() 问题

Question

I have been running into this funny issue with using atoi() in C for an assignment. Im gonna paste a bit of the code I have so far...

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define _CRT_SECURE_NO_WARNINGS
 char RimDiameter[15];
 char TireCode[15];
int x;
 puts("Enter the code on the Tire");  // P215/65R15 95H
gets(TireCode);
strncpy(RimDiameter, TireCode+8, 2); // TireCode = P215/65R15 95H, RimDiameter = 15
int x = atoi(RimDiameter);    // where I'm having issues
 if(x >=14 && x <=22)
{
 printf("%c is valid\n", x);
}
else
{
printf("%c is invalid\n", x);
}

I'm using strncpy() to help grab the numbers I need in the string and copy them to RimDiameter. I should have '15' stored in RimDiameter but once I use atoi(RimDiameter) I get 0 stored in x instead of '15' which is needed for my if/else statements to work properly.

Anyone have any idea why I would be getting this issue?

Answer 1

This is a place where sscanf is really useful:

int p, r, d, h;
char TireCode[256];

fputs("Enter the code on the tire: ", stdout);
if (!fgets(TireCode, sizeof(TireCode), stdin)) {
    fprintf(stderr, "Unexpected EOF");
} else if (sscanf(TireCode(" P%d /%dR%d%d", &p, &r, &d, &h) == 4) {
    if (d >= 14 && d <= 22) {
        printf("%d is valid\n");
    } else {
        printf("%d is invalid\n");
    }
} else {
    fprintf(stderr, "Input is not in the expected format");
}

You can try multiple different patterns of letters/numbers to see which one matches with an if...else if...else if... chain