如何在C中刷新输入流? [英] How can one flush input stream in C?

问题描述

我在这里不能刷新 stdin ，有什么方法可以刷新它吗?如果不是，那么如何使getchar()接受用户输入的字符，而不是输入缓冲区中scanf()留下的"\ n"?

I am not able to flush stdin here, is there a way to flush it? If not then how to make getchar() to take a character as input from user, instead of a "\n" left by scanf() in the input buffer??

#include "stdio.h"
#include "stdlib.h"

int main(int argc,char*argv[]) {
    FILE *fp;
    char another='y';
    struct emp {
        char name[40];
        int age;
        float bs;
    };
    struct emp e;
    if(argc!=2) {
        printf("please write 1 target file name\n");
    }
    fp=fopen(argv[1],"wb");
    if(fp==NULL) {
        puts("cannot open file");
        exit(1);
    }
    while(another=='y') {
        printf("\nEnter name,age and basic salary");
        scanf("%s %d %f",e.name,&e.age,&e.bs);
        fwrite(&e,sizeof(e),1,fp);

        printf("Add another record (Y/N)");
        fflush(stdin);
        another=getchar();
    }
    fclose(fp);
    return 0;
}

更新的代码，仍然无法正常工作

updated code, still not working properly

#include "stdio.h"
#include "stdlib.h"

int main(int argc,char*argv[]) {
    FILE *fp;
    char another='y';
    struct emp {
        char name[40];
        int age;
        float bs;
    };
    struct emp e;
    unsigned int const BUF_SIZE = 1024;
    char buf[BUF_SIZE];

    if(argc!=2) {
        printf("please write 1 target file name\n");
    }
    fp=fopen(argv[1],"wb");
    if(fp==NULL) {
        puts("cannot open file");
        exit(1);
    }
    while(another=='y') {
        printf("\nEnter name,age and basic salary : ");
        fgets(buf, BUF_SIZE, stdin);
        sscanf(buf, "%s %d %f", e.name, &e.age, &e.bs);
        fwrite(&e,sizeof(e),1,fp);
        printf("Add another record (Y/N)");
        another=getchar();
    }
    fclose(fp);
    return 0;
}

输出:

dev@dev-laptop:~/Documents/c++_prac/google_int_prac$ ./a.out emp.dat

Enter name,age and basic salary : deovrat 45 23
Add another record (Y/N)y

Enter name,age and basic salary : Add another record (Y/N)y

Enter name,age and basic salary : Add another record (Y/N)

推荐答案

更新:您需要在循环末尾添加另一个getchar()，以消耗Y/N后的'\ n'.我认为这不是最好的方法，但是它将使您的代码按现在的样子工作.

Update: You need to add another getchar() at the end of your loop to consume the '\n' that follows the Y/N. I don't think this is the best way to go, but it will make your code work as it stands now.

while(another=='y') {
    printf("\nEnter name,age and basic salary : ");
    fgets(buf, BUF_SIZE, stdin);
    sscanf(buf, "%s %d %f", e.name, &e.age, &e.bs);
    fwrite(&e,sizeof(e),1,fp);
    printf("Add another record (Y/N)");
    another=getchar();
    getchar();
}

我建议将要解析的数据(最多包含'\ n')读入缓冲区，然后使用sscanf()解析出来.这样，您就消耗了换行符，并且可以对数据执行其他完整性检查.

I would suggest reading the data you want to parse (up to and including the '\n') into a buffer and then parse it out using sscanf(). This way you consume the newline and you can perform other sanity checks on the data.

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