txt file from ofstream. Increment the files name?

This is a discussion on txt file from ofstream. Increment the files name? within the C++ Programming forums, part of the General Programming Boards category; Hi all I'm trying to generate some text files and have the name of each file created increment or be ...

  1. #1
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    txt file from ofstream. Increment the files name?

    Hi all

    I'm trying to generate some text files and have the name of each file created increment or be random (doesn't matter which), but am having difficult as the way I know of creating txt files is by placing the name of the file between double quotes. I have tried replacing the name part with rand(), and also by placing a variable where the name appears and then incrementing the value of the variable on each iteration of the loop (variablename++).

    Both failed.

    Here is my code, pretty standard:

    Code:
    #include <iostream>
    #include <fstream>
    #include <cstdlib>
    using namespace std;
    
    void main()
    {
    	for(int a =0;a<99;a++)
    	{
    
    		ofstream out("WantToIncrementThis");
    		if(!out)
    		{
    			cout << "cannot open file";
    		}
    		out << rand() << rand() << rand()<< rand() << rand() << rand()<< rand() << rand() << rand();
    
    		out.close();
    	}
    	system ("pause");
    }
    So I just wondering how I should go about this.

    Many thanks for any help1!

    Swerve

  2. #2
    Kernel hacker
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    You'll have to generate a string with the number in it - for example using stringstream or sprintf.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    and the Hat of Guessing tabstop's Avatar
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    14,185
    "Print" a string (using stringstreams, for instance), and then use string.c_str() in the ofstream constructor.

    There's also tmpnam in ... cstdio, I guess.

  4. #4
    deletedforumuser
    Guest
    Example:

    Code:
    	char Filename[256] = "File";
    
    	for(int i = 0; i < 10; i++)
    	{
    		sprintf_s(Filename,"File%d",i+1);
    		cout << Filename;
    	}

  5. #5
    Banned master5001's Avatar
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    Or if you want to be standard C...

    Example:
    Code:
    	char Filename[256];
    
    	for(int i = 0; i < 10; i++)
    	{
    		std::snrintf(Filename, sizeof(Filename), "File&#37;02d",i+1);
    		std::printf("%s\n", Filename);
    	}
    The extra arguments I put in there are because I like my files to be listed numerically in order.

    There is a more C++ approach to this using stringstreams.

    Example:
    Code:
    #include <sstream>
    
    //... later in your code
    
    std::stringstream Filename;
    
    for(int i = 0; i < 10; ++i)
    {
      Filename.clear();
      Filename << "File";
      Filename.fill('0');
      Filename.width(2);
      Filename << i;
      std::cout << Filename.str().c_str() << std::endl;
    }

  6. #6
    C++まいる!Cをこわせ!
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    http://cpwiki.sf.net/void_main
    Void main is non-standard and should not be used.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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