[英]How can I find a line in a text file and replace it?
我正在為一個大學項目工作,該項目要求我在文本文件中找到一個值,然后用存儲在float變量中的新值替換它,部分問題是我不知道所需的項目僅在替換位置(例如,我可以搜索值為0.00,但多條記錄可以具有該余額)。
文本文件的布局如下:
用戶名1
密碼1
帳號1
平衡1
吉米54
FooBar123
098335
13.37
...
我的代碼的相關部分如下所示:
用戶輸入用戶名,我們將其存儲在enterName中
#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
cout << "Please enter your username:\n";
cin >> enteredName;
在代碼中向下大約100行,我們到達了對該問題重要的部分:
if (c2 == 1)
{
//irrelevant to problem
}
else if (c2 == 2)
{
float convBal;
float deposit;
string newBal;
convBal = ::atof(ball.c_str());
/* Ball is declared higher up in the code and just contains a
value pulled from the text file for the sake of the question
we'll say it has a value of 0.00 */
cout << "How much would you like to deposit?:\n";
cin >> deposit;
newBal= convBal + deposit;
cout << "Your total balance is now: "<< newBal << "\n\n";
}
}
因此,從這里開始需要做的是打開文件,在文件中搜索enterName(在這種情況下,我們稱Jimmy54),然后用存儲在newBal中的值替換用戶名(13.37)下方的三行值。
提前致謝! 抱歉,如果這聽起來像是一個愚蠢的問題,我對編程還是相當陌生的,對於c ++來說還是比較新的
編輯#1:這是我到目前為止的代碼,它找到entryName,然后獲取下面的3行:
if (myfile.is_open())
{
while (getline(myfile, line))
{
if (line.compare(enteredName) == 0)
{
getline(myfile, line); //Password
getline(myfile, line); //Account Number
getline(myfile, line); //Balance
}
}
}
myfile.close();
這是解決我的問題的代碼,雖然有點草率,但是可以正常工作!
它只是讀入一個新文件並進行任何更改,然后再次寫回。
if (myfile.is_open())
{
while (getline(myfile, line))
{
if (line.compare(enteredName) == 0)
{
tempFile << enteredName << "\n"; //Username
getline(myfile, line);
tempFile << line << "\n"; //Password
getline(myfile, line);
tempFile << line << "\n"; //Account Number
getline(myfile, line);
tempFile << newBal << "\n"; //Balance
}
else
{
tempFile << line << "\n"; //Username
getline(myfile, line);
tempFile << line << "\n"; //Password
getline(myfile, line);
tempFile << line << "\n"; //Account Number
getline(myfile, line);
tempFile << line << "\n"; //Balance
}
}
}
myfile.close();
tempFile.close();
/* Had to declare these again beacuse the compiler was throwing some bizarre error when using the old declarations */
ifstream tempF("TempStore.csv");
ofstream mainF("DataStore.csv", ios::trunc);
//Writes back from TempStore to DataStore with changes made correctly
if (tempF.is_open())
{
while (getline(tempF, line))
{
mainF << line << "\n"; //Username
getline(tempF, line);
mainF << line << "\n"; //Password
getline(tempF, line);
mainF << line << "\n"; //Account Number
getline(tempF, line);
mainF << line << "\n"; //Balance
}
}
tempF.close();
mainF.close();
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