C语言怎么吧字符串 [123,456]中的字符123和456转化成数字123和456？

#include <stdio.h>
main()
{
    char s[]="123,456";
    char *p=s;
    int a, n;
    while (*p)
    {
        if (sscanf(p,"%d%n",&a,&n) == 1)
        {
            printf("%d\n", a);
            p += n;
        }
        else
            ++p;
    }
}

#include <stdio.h>
main()
{
    char s[]="123,456";
    int a, b;
    sscanf(s,"%d,%d",&a,&b);
    printf("a=%d\nb=%d\n", a, b);
}

atoi()函数了解一下