c - 如何对输入进行验证？数字或字母..C 编程

Question

set1:
printf("Name            : ");
gets (name);
if (isalpha(name)) {printf("\nSorry, input is invalid\n");
goto set1;}

这是我的一段代码，我将 name 声明为 char name [30]；但是，它说 *char 类型的错误参数与 int 类型的参数不兼容。如何验证我们是否随机输入字母和数字(例如 gghjhj88888)？

谢谢你的帮助？

Answer 1

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int isdigits(char *s){
    //return value : true if the string is all numbers.
    while(*s)
        if(!isdigit(*s++))
            return 0;
    return 1;
}

int main(void){
    char dateOfBirth[7];
    int len;
set4:
    printf("Date of Birth (DDMMYY)  : ");
    //Doesn't accept input more than specified number of characters
    fgets(dateOfBirth, sizeof(dateOfBirth), stdin);
    rewind(stdin);//keyborad buffer flush
    //fflush(stdin);//discard the character exceeding the amount of input
    //How fflush will work for stdin by the processing system (that is undefined)
    //while ('\n' != fgetc(stdin));//skip if over inputted
    len = strlen(dateOfBirth);
    if(dateOfBirth[len-1] == '\n') dateOfBirth[--len] = '\0';//newline drop
    if(len != 6 || !isdigits(dateOfBirth)){
        printf("\nSorry, input is invalid\n");
        goto set4;
    }

    return 0;
}