从键盘输入取并插入一个二进制文件 [英] Take input from keyboard and insert in a binary file

问题描述

我试图写一个函数来获得输入从用户的结构的形式，将其插入一个二进制文件。 （足球结果）用户输入 teamA ， teamB ， goalsA 和 goalsB 当我尝试以显示我已经进入，我没有得到正确的结果。我究竟做错了什么？
code：

 无效addResult（）
{
    结构匹配匹配;
    字符输入[100];
    FILE *文件1;    文件1 = FOPEN（matches.bin，RW + B）;
    的printf（请输入要添加到文件\\ n个resulst）;
    scanf函数（％S，输入）;    而（！的feof（文件1））
        FREAD（安培;匹配的sizeof（匹配），1，文件1）;
    fseek的（文件1，sizeof的（比赛），SEEK_END）;
    FWRITE（安培;输入的sizeof（匹配），1，文件1）;
    fflush（文件1）;
    FCLOSE（文件1）;    文件1 = FOPEN（matches.bin，R）;
    而（！的feof（文件1））{
        FREAD（安培;匹配的sizeof（匹配），1，文件1）;
        的printf（％s％S％I％I \\ N，match.teamA，match.teamB，match.goalsA，match.goalsB）;
    }
    FCLOSE（文件1）;
}
 

解决方案

你的方法的主要问题是，由用户输入的字符串必须转换为结构的匹配在某些时候。这样做是在C的烦人尴尬的任务：您需要先拆分用户输入空格分隔的单词或类似的，得到的字符串重新presentations为 .teamA ， .teamB ， .goalsA 和 .goalsB （的例如的使用功能首页从＆LT; strings.h＆GT; ），然后你需要将目标数字的字符串重新presentations使用的atoi 函数从＆LT转换成整数值; stdlib.h中＆GT; 。

一旦你有了新的数据作为结构的匹配，可以使用如下命令追加新的结构到文件中：

 文件1 =的fopen（matches.bin，A + B）;
FWRITE（安培; inputAsStruct，sizeof的（比赛），1，文件1）;
 

文件模式 A + 打开用于读取和写入文件，创建如果需要一个新的文件，并确保写入是在末尾。

要输出不需要关闭并重新打开该文件中的记录。你可以只用 fseek的将文件移动位置回到文件的开头：

  fseek的（文件1，0，SEEK_SET）;
 

最后，正如其他人所指出的，的feof 可能无法检测到文件末尾可靠。我相信它只能保证后，因为它已经达到文件末尾的 FREAD 失败了一次，所以你应该检查 FREAD <返回值工作/ code>代替。

I am trying to write a function to take input from user in the form of a struct and insert it into a binary file. (of football results) the user is to enter teamA, teamB, goalsA and goalsB When I try to display what I have entered, I am not getting the correct result. What am I doing wrong? Code:

void addResult()
{
    struct matches match;
    char input[100];
    FILE * file1;

    file1 = fopen("matches.bin","rw+b");
    printf("Enter the resulst you want to add to the file\n");
    scanf("%s",input);

    while(!feof(file1))
        fread(&match,sizeof(match),1,file1);
    fseek(file1,sizeof(match),SEEK_END);
    fwrite(&input,sizeof(match),1,file1);
    fflush(file1);
    fclose(file1);

    file1 = fopen("matches.bin","r");
    while(!feof(file1)) {
        fread(&match,sizeof(match),1,file1);
        printf("%s %s %i %i\n",match.teamA,match.teamB,match.goalsA,match.goalsB);
    }
    fclose(file1);
}

解决方案

The main problem with your approach is, that the string inputted by the user must be converted to a struct matches at some point. Doing so is an annoyingly awkward task in C: you will need to first split the user input into space-separated words or similar, to get string representations for .teamA, .teamB, .goalsA and .goalsB (e.g. using the function index from <strings.h>), and then you need to convert the string representations of the goal numbers into integer values using the atoi function from <stdlib.h>.

Once you have the new data as a struct matches, you can append the new struct to the file using commands like the following:

file1 = fopen("matches.bin", "a+b");
fwrite(&inputAsStruct, sizeof(match), 1, file1);

The file mode a+ opens the file for reading and writing, creates a new file if needed, and ensures that writes are appended at the end.

To output the records you don't need to close and re-open the file. You can just use fseek to move the file position back to the start of the file:

fseek(file1, 0, SEEK_SET);

Finally, as others pointed out, feof may not detect the end of file reliably. I believe it is only guaranteed to work after the fread failed once because it reached the end of file, so you should check the return value of fread instead.

这篇关于从键盘输入取并插入一个二进制文件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！