如何逐行更新结构文本文件

Question

我的代码将所有活动详细信息存储在一个文件中，我在使用 id 搜索访问该文件中的数据时遇到问题。这是我的添加活动函数和结构。

struct activities{
    char id[5];
    char actName[200];
    char date[20];
    char day[20];
}act;

//function to add volunteering activities
void addAct(){
    FILE *fileAct;
    
    //prompt user to enter activities details
    printf("\n\t Planning Volunteering Activities");
    printf("\n\t -----------------------------------");
    printf("\n\t Program ID \t: ");
    scanf(" %[^\n]%*c", &act.id);
    printf("\t Name of Activity : ");
    scanf(" %[^\n]%*c", &act.actName);
    printf("\t Date \t\t: ");
    scanf(" %[^\n]%*c", &act.date);
    printf("\t Day \t\t: ");
    scanf(" %[^\n]%*c", &act.day);
    
    //create & write in file activity
    fileAct = fopen("Activity", "a");
    
    fprintf(fileAct, "\n\t %s \n", act.id);
    fprintf(fileAct, "1. Name of Activity : %s \n", act.actName);
    fprintf(fileAct, "2. Date : %s \n", act.date);
    fprintf(fileAct, "3. Day : %s \n", act.day);
    
    //close file activity
    fclose(fileAct);
}

这是我的更新功能。

void updateAct(){
    //variable declaration
    char progID[5];
    
    //open activity file
    FILE *fp = fopen ("Activity", "r");
    
    //prompt user to search activities to update
    printf("\t Search by Program ID : ");
    scanf(" %[^\n]%*c", &progID);
   
    while( !feof(fp)){
        fread (&act, sizeof(struct activities), 1, fp);
        
        if (strcmp(progID, act.id) == 0)
            printf("%s %s", act.id, act.actName);
    }
    fclose(fp);
}
    

在上面的更新函数中，我无法根据用户搜索访问struct中的act.id，而是程序将整个数据显示在文件中。如何解决这个问题？

Answer 1

您提供指向 char 数组的指针，从技术上讲，它是指向指针的指针。但是scanf只需要指针。

删除scanf()-调用中的&，并为格式参数添加最大长度说明符：

改变

scanf(" %[^\n]%*c", &progID);

到

scanf(" %4[^\n]%*c", progID);

对于一个 5 字节的缓冲区。

Answer 2

void readLine(char* message, char* buffer, int buffer_size)
{
    printf("\t%s: ", message);
    fgets(buffer, buffer_size, stdin);
    // fgets inserts '\n' at the end
    // we are removing it
    buffer[strlen(buffer) - 1] = '\0'; 
}

void addAct(){
    FILE *fileAct;
    struct activities newAct;
    //prompt user to enter activities details
    printf("\n\tPlanning Volunteering Activities");
    printf("\n\t-----------------------------------\n");

    readLine("Program ID", newAct.id, sizeof(newAct.id));
    readLine("Name of Activity", newAct.actName, sizeof(newAct.actName));
    readLine("Date", newAct.date, sizeof(newAct.date));
    readLine("Day", newAct.day, sizeof(newAct.day));

    //create & write in file activity
    fileAct = fopen("Activity", "ab+");
    if(NULL != fileAct) {
        fwrite(&newAct, sizeof(struct activities), 1, fileAct);
        //close file activity
        fclose(fileAct);
    }
}

void updateAct(){
    //variable declaration
    char progID[5];
    struct activities readAct;
    //open activity file
    FILE *fp = fopen("Activity", "rb");
    if(NULL != fp) {
        //prompt user to search activities to update
        printf("\tSearch by Program ID : ");
        fgets(progID, sizeof(progID), stdin);
        progID[strlen(progID) - 1] = '\0';
        while(fread(&readAct, sizeof(struct activities), 1, fp) != 0){
            if (strcmp(progID, readAct.id) == 0)
            {
                printf("%s %s\n", readAct.id, readAct.actName);
                break;
            }
        }
        fclose(fp);
    }
}