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help on writing to a file.

Posted on 2001-08-09
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Last Modified: 2010-04-02
I'm relatively new to C++, and was wondering how it was possible to write to a created temp file, so that my program can read from it when my program loads so it can gain information written to the file.
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Question by:bobbygordon
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andysalih earned 600 total points
ID: 6370548
this explains how to write a file in .txt format, well write information to the file

ofstream fout;


That?s all for that, but to open the file, you must call ofstream::open() like this.


fout.open("output.txt");


You could have also just as well opened the file as you declared the stream by passing the filename as a parameter to the constructor of the object.


ofstream fout("output.txt");


This will be our selected method of declaring objects, since it?s still rather simple to see how to create and open the file. By the way, if the file you are opening for output does not exist, it will be created for you, so there is no need to ever worry about creating the file. Now to output to the file, it works exactly like how you would output to "cout." For those of you that don?t know "cout" for console output, then here?s an example.


int num = 150;
char name[] = "John Doe";
fout << "Here is a number: " << num << "\n";
fout << "Now here is a string: " << name << "\n";


Now to save the file, you must close the file, or flush the buffer to the file. Closing the file will not let you access it anymore, so only call it when you are done using the file and it will automatically save the file for you. Flushing the buffer will write the buffer to the file and still keep the file open, so use this function when necessary. Flushing is done by another output looking call, and closing is done by a method call. Like this:


fout << flush;
fout.close();


Now the contents of the file when you open it in a text editor will read:


Here is a number: 150
Now here is a string: John Doe

cheers
Andy
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Expert Comment

by:andysalih
ID: 6370572
this is how you would read it back in

ifstream fin("filename.txt");
int number;
char letter, word[8];
fin >> number;fin >> word;


hope that helps

andy

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Author Comment

by:bobbygordon
ID: 6370600
What header file would i need to include that contains this ofstream and fout?
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Expert Comment

by:trongnghia
ID: 6370800
This's header file:

#include <fstream.h>

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Author Comment

by:bobbygordon
ID: 6370820
I just increased the points...

Is there a way to write and recieve this data, to and from a database as opposed to just a text file?

Or is there a way to use the text file as a database?
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by:IainHere
ID: 6371917
A technicality: the header file should be <fstream> - it puts the declarations in the std namespace.

There are many ways to read and write to a database.  It will probably (almost certainly) entail more work than using a textfile.  If you intend to distibute your application, you'd also need to distribute the database. The methods you use will depend on the database you intend to use, and depending on the amount/type of info it might be a complete overkill.

You already are using the text file as a database - it's just a very primitive and non-standard one.

If you still want to go down the database path (which would be a good idea if you're storing lots of info), you'll need to post more details.
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Author Comment

by:bobbygordon
ID: 6373127
For the details that I gave, this helped me understand the concept fairly well.

Thanks,
-Bobby Gordon
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