File I/O, integers in the file name

This is a discussion on File I/O, integers in the file name within the C++ Programming forums, part of the General Programming Boards category; I want to read a file, change the data and create say 50 new files from the original file, all ...

  1. #1
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    File I/O, integers in the file name

    I want to read a file, change the data and create say 50 new files from the original file, all numbereder 1 to 50.

    So let's say that the original file is called "file.txt" then I want the others to be named "file1.txt" to "file50.txt". The number will be int x and I will have a loop until x > 50. The number may change.

    How do I do this? I figured out how to use a string variable as a filename. I tried to see how I can create a new string out of a string and a integer but I can't figure out how to do that.

    Oh, I am currently using iostream.

    Thanks.

  2. #2
    CSharpener vart's Avatar
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    To create new string from the other - use stringstream
    Code:
    #include<string>
    #include<sstream>
    #include <iostream>
    
    int main(int argc,char  *argv[])
    {
    	std::string text("test");
    	std::stringstream buffer;
    	buffer << text << 5 <<".txt";
    	text  = buffer.str();
    	std::cout << text;
    
    	return 0;
    }
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #3
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    Code:
    #include <iostream>
    #include <string>
    #include <algorithm>
    #include <sstream>
    
    using namespace std;
    
    
    int main ()
    {
    	ostringstream out;
    	
    	string str = "file";
    	int num = 1;
    	
    	out<<str<<num<<".txt";
    
    	cout<<out.str()<<endl;
    
    	return 0;
    }

  4. #4
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    vart's code added the filenames together. Each time through the loop the name of the file became longer. First file is called "offspring1.txt", the second "offspring1.txtoffspring2.txt" etc.


    Now maybe I am stupid but I couldn't figure out a way to clear the string each time through the loop. So I switched to 7stud. That gave an error. So I added a buffer like vart's code has:

    Code:
    string offspring_file_name;
    ostringstream buffer;
         
    buffer<<"offspring"<<z<<".txt";
         
    offspring_file_name = buffer.str();
         
         
    offspring_file.open (offspring_file_name.c_str());

    This seems to work.

  5. #5
    CSharpener vart's Avatar
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    Quote Originally Posted by Prometheus
    vart's code added the filenames together. Each time through the loop the name of the file became longer. First file is called "offspring1.txt", the second "offspring1.txtoffspring2.txt" etc.


    Now maybe I am stupid but I couldn't figure out a way to clear the string each time through the loop.
    Sure not my code - my code has no loops.

    move stringstream declarartion into the loop. This will construct/destruct variable on each iteration effectively clearing it
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  6. #6
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    Now maybe I am stupid but I couldn't figure out a way to clear the string each time through the loop
    Code:
    string str = "hello";
    
    cout<<str<<endl;
    str = "";
    cout<<str<<endl;
    Code:
    ostringstream out;
    
    out<<"hello world "<<3;
    cout<<out.str()<<endl;
    
    out.str("");
    cout<<out.str()<<endl;
    Note: the str() method can be used to get and set the value of the stringstream.
    Last edited by 7stud; 01-18-2007 at 11:21 AM.

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