将结构数组放入文件并读取它

Posted 2023-02-18

【中文标题】将结构数组放入文件并读取它

【英文标题】：Putting struct array into file and reading it

【发布时间】：2021-03-15 23:01:22

【问题描述】：

我想将一个结构数组放入一个文件中，并将一个整数放入同一个文件中（我想对数组使用 fwrite()）。当我尝试阅读它时，似乎出现了问题。我是 C 的新手，所以也许你可以向我解释它是如何工作的。提前致谢。

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

typedef struct Data

    char street[40];
    char building[10];
    char email[30];
    unsigned long long number;

Data;

int main()

    Data data[3];
    Data output[3];
    int size = 2;
    int sizeout;
    // putting something inside
    strcpy(data[0].building, "11");
    strcpy(data[0].email, "a@a.a");
    data[0].number = 37068678102;
    strcpy(data[0].street, "Street1");

    strcpy(data[1].building, "21");
    strcpy(data[1].email, "b@b.b");
    data[1].number = 37068678432;
    strcpy(data[1].street, "Street2");

    //writing into file (I want to use "wb")
    FILE *write;
    write = fopen("temp.bin","wb");
    //if I understand correctly, fprintf is the way to put in an integer
    fprintf(write,"%d",size);
    //putting array in
    fwrite(data,sizeof(Data),2,write);
    fclose(write);



    FILE *read;
    fseek(read, 0, SEEK_SET);

    read = fopen("temp.bin","rb");
    //gettinf the int out
    fscanf(read,"%d",&sizeout);
    //getting array out
    fread(output,sizeof(Data),2,read);
    fclose(read);

    //printing what I got
    for(int i = 0; i < sizeout; ++i)
        printf("First struct: %s %s %s %llu\n", output[i].building, output[i].email, output[i].street, output[i].number);
    
    return 0;

【问题讨论】：

你在read指针上调用fseekfopen之前。

@user3121023 如果我使用 fwrite 整数它会崩溃，至于 data[0] 这是一个疏忽，无论如何谢谢:)

【参考方案1】：

这是您的代码，但更简洁。这家伙说的是真的

你在fopen之前的读指针上调用fseek。

但这也不是必需的，因为当您在r中打开文件时，指针将始终位于第一个位置

#include <stdio.h>
#include <windows.h>
#include <stdlib.h>
#include <conio.h>
#define doc "doc.bin"

typedef struct Data

    char street[40];
    char building[10];
    char email[30];
    unsigned long long number;

Data;

int sizeofdata =  sizeof(Data);


int main()



FILE *f;

f = fopen(doc, "wb"); //if you want to open it in w remember that all that is contained with in will be erased , i recomend a+b

      Data data[3];
    Data output[3];
    int size = 2;
    int sizeout;
    // putting something inside
    strcpy(data[0].building, "11");
    strcpy(data[0].email, "a@a.a");
    data[0].number = 37068678102;
    strcpy(data[0].street, "Street1");

     fwrite(&data, sizeofdata,1, f);//the one represents the quantitie of regiesteres you wanna imput , you can make it a variable

     fclose(f);


     if ((f=fopen(doc,"rb"))!=NULL)//this makes for a cleaner solution it will be simpeler in the long run
            while (!feof(f)) 
            fread(&output, sizeofdata,1, f);
            if (!feof(f))
               printf("First struct: %s %s %s %llu\n", output[0].building, output[0].email, output[0].street, output[0].number);