Using variables in fstream

This is a discussion on Using variables in fstream within the C++ Programming forums, part of the General Programming Boards category; does anybody know how to use a variable when declaring an fstream file? Here's what I want to do: //this ...

  1. #1
    Kiss the monkey. CodeMonkey's Avatar
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    Question Using variables in fstream

    does anybody know how to use a variable when declaring an fstream file? Here's what I want to do:

    //this code is just an example, not a problem
    for (x=0; x <10;x++)
    {
    ofstream file("file(x).txt");
    file<<"Hi, peeps!";
    file.close();
    }

    this code would create ten files, each named file(x) (x being a number 1-10).

    How can I do this?
    "If you tell the truth, you don't have to remember anything"
    -Mark Twain

  2. #2
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    you need to change x to a string using itoa() --it's in coni0.h-- if you have it or sprintf. Then append to a string with the file name and then append the file extension. Do your file thingy. Then reset the initial string. Something like this:

    char fileName[18] = "file";
    char addOn[3];
    char extension[5] = ".txt:;
    for (x=0; x <10;x++)
    {
    itoa(x, addOn, 10);
    strcat(fileName, addOn);
    strcat(fileName, extension)
    ofstream file(fileName);
    file<<"Hi, peeps!";
    file.close();
    strcpy(fileName, "file");
    }

  3. #3
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    a (slightly easier to read) version of this would be as follows (the principle is exactly the same, this just takes fewer commands):
    Code:
    char fileName[20];
    for (x = 0; x < 10; x++){
    	sprintf((char *)&fileName,"file%d.txt",x);
    	ofstream file(fileName);
    	file<<"Hi, peeps!";
    	file.close();
    }

  4. #4
    and the hat of int overfl Salem's Avatar
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    Or without the cast (and incorrect use of &)
    &nbsp; sprintf(fileName,"file%d.txt",x);

    &fileName has a type of char (*)[20] (pointer to an array), which is why you needed the cast.
    fileName has a type of char *(pointer to the first element), which is what sprintf (and most string functions in general) expect.
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  5. #5
    Kiss the monkey. CodeMonkey's Avatar
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    I have conio.h, but my compiler still game me an error on itoa.
    "If you tell the truth, you don't have to remember anything"
    -Mark Twain

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