编辑和删除文件C / C ++中的数据 [英] Edit and delete data in file C/C++

问题描述

Hellow！

我想在文件（C / C ++）中编辑和删除数据。< br $> b $ b

我尝试了什么：



我试过这种方法

 ifstream read，read1; 
 ofstream write，write1; 
 
 read.open（  File.txt，ios :: < span class =code-keyword> in ）; 
 write.open（  Temp.txt）; 
 
  int  old，New，a; 
 cout<<  输入您要编辑的编号=; 
 cin>>旧; 
 
 cout<<  输入要替换的新号码; 
 cin>>新; 
 
  while （！read.eof（））{
 read>>一个; 
 
  if （a == old）{write<<新<< ENDL; } 
  else  {write<< a<< ENDL; } 
} 
 
 read.close（）; 
 write.close（）; 
 
 read1.open（  Temp.txt，ios :: app ）; 
 write1.open（  File.txt）; 
 
  while （！read1.eof（））{
 read1>>一个; 
 write1<< a<< ENDL; 
} 
 

此代码运作良好。

但问题是这个过程很慢。我的意思是如果文件中有数千行，我想编辑或删除一行，那么过程非常慢。

所以我需要一些算法，我可以编辑或删除只是我想要的那条线。

那么有没有算法或函数？



谢谢！

解决方案

您可以避免仅复制内容的第二个while循环。而是删除 File.txt ，然后重命名 Temp.txt ：

  //  只有使用过的C库 
  // <才需要删除文件/ span> 实现不支持重命名为现有文件 
 remove（  file.txt的）; 
重命名（  Temp.txt，   File.txt）; 

这将使您的应用程序运行大约一半的大型文件代码。

我会做以下事情：



1）以字符串形式阅读完整文件

2 ）制作比字符串替换

3）并写入文件



使用std :: string来支持我的计划; - ）

Hellow!
I want to edit and delete data in file(C/C++).

What I have tried:

I have tried this method

 ifstream read, read1;
ofstream write, write1;

read.open("File.txt", ios::in);
write.open("Temp.txt");

int old, New, a;
cout << "Enter number you want to edit = ";
cin >> old;

cout << "Enter new number to replace ";
cin >> New;

while (!read.eof()) {
    read >> a;

    if (a == old) { write << New << endl; }
    else          { write << a << endl;   }
}

read.close();
write.close();

read1.open("Temp.txt", ios::app);
write1.open("File.txt");

while (!read1.eof()) {
    read1 >> a;
    write1 << a << endl;
}

And this code work well.
But the issue is that this process is very slow. I mean if there are thousand of lines in file and i want to edit or delete just one line then the process is very slow.
So i need some algorithm by using that i can able to edit or delete just that line i want.
So is there any algorithm or Function?

Thanks!

解决方案

You can avoid the second while loop which is just copying the content. Instead delete File.txt and then rename Temp.txt:

// Deleting the file is only necessary if the used C library 
//  implementation does not support renaming to an existing file
remove("File.txt");
rename("Temp.txt", "File.txt");

That will make your application run about half the time of your code with large files.

I would do the following:

1) read the full file in a string
2) make than a string replace
3) and write the file

use std::string for supporting my plan ;-)

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