Question

我有一个c ++程序来获取issuance.csv文件的最后一行数据（有id，日期，时间）并在其上写新记录但是当我尝试在其上写入新数据（如id，时间，日期）时，保存空白行，而不在issu.c.c文件上存储数据，我该怎么办？

#define DEFAULT_ID "2000"
#define ISSUE_FILE_ADDRESS "/home/pi/file/issuance.csv"

int WriteNewRecord(string NewID, string NewCustomerID, string NewIssueDate)
{
    fstream FileStream;
    FileStream.open(ISSUE_FILE_ADDRESS, fstream::app | fstream::out);//Just for write into file
    if(!FileStream.is_open())
    {
        cout << "File Open Error1" << endl;
        return -1;
    }
    FileStream << NewID << "," << NewCustomerID << "," << NewIssueDate  << endl;//Just for write into file
    FileStream.close();
    return 0;
}
int GetLastData(string& LastID, string& LastCustomerID, string& LastDate, string& LastTime)
{
    fstream FileStream;
    FileStream.open(ISSUE_FILE_ADDRESS, fstream::in);
    if(!FileStream.is_open())
    {
        cout << "File Open Error2" << endl;
        return -1;
    }
    string Line;
    int Indices[3];
    getline(FileStream, Line);
    if(Line.length())
    {
        do {
            Indices[0] = Line.find(",");
            Indices[1] = Line.find(",", Indices[0] + 1);
            Indices[2] = Line.find(",", Indices[1] + 1);

            LastID = Line.substr(0, Indices[0]);
            LastCustomerID = Line.substr(Indices[0] + 1, Indices[1] - Indices[0] - 1);
            LastDate = Line.substr(Indices[1] + 1, Indices[2] - Indices[1] - 1);
            LastTime = Line.substr(Indices[2] + 1, Line.length() - Indices[2] - 1);
            getline(FileStream, Line);

        } while (Line.length());
    }
    else
        LastID = DEFAULT_ID;

    FileStream.close();
    return 0;
}
int time(){
     time_t currentTime;
      struct tm *localTime;

      time( &currentTime );                   // Get the current time
      localTime = localtime( &currentTime );  // Convert the current time to the local time

      int Day    = localTime->tm_mday;
      int Month  = localTime->tm_mon + 1;
      int Year   = localTime->tm_year + 1900;
      int Hour   = localTime->tm_hour;
      int Min    = localTime->tm_min;
      int Sec    = localTime->tm_sec;
      cout  << Day << "/" << Month << "/" << Year << ", "<< Hour << ":" << Min << ":" << Sec<<endl;
      //std::cout  << std::endl;

      return (currentTime);
}


int main()
{
    string ID,CustomerID,Date,Time;
    if(!GetLastData(ID, CustomerID, Date,Time))
    {
        cout << ID << " " << CustomerID << " " << Date << " " << Time << endl;
        //Issuance Operation...
        //...
        //...
//      if(!WriteNewRecord("2008", "100000", "4/29/2015" , "10:55:15"))//Example for test
         string NewID,NewCustomerID,NewIssueDate;
    if(!WriteNewRecord(NewID, NewCustomerID, NewIssueDate))
        {
        unsigned int new_id = atoi(ID.c_str()) + 1;
        char tmp[5];
        sprintf(tmp, "%d", new_id);
        NewID = string(tmp);
        tmp[4] = 0;
        NewCustomerID=CustomerID;
        char write[4];
           unsigned int new_date=time();
            memcpy(write,&new_date,2);
            //cout << write << endl;
            sscanf ( NewIssueDate.c_str(), "%d", &new_date );

                      cout<< NewIssueDate<<"," << NewCustomerID<<","<< NewID <<endl;

            //cout << NewIssueDate<<endl;

            return 0;

        }
    }
}

Answer 1

如果您查看代码，则执行

string NewID,NewCustomerID,NewIssueDate, NewIssueTime;
if(!WriteNewRecord(NewID, NewCustomerID, NewIssueDate))
{
    // Initialize variable but don't write them to the file
}

当您声明std::string变量时，它们被初始化为空，因此将它们写入文件将不会写入任何内容。在将变量写入文件后，然后初始化变量。

Answer 2

您可以在编写

之前尝试使用

div {
    width: 150px;
    height: 150px;
    overflow: scroll;
}

获取最后一行文件并在其上写下新记录

2 个答案: