Reading from a textfile with unknown length?

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  1. #1
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    Reading from a textfile with unknown length?

    [c++] Need help with pointers?
    Hi I want to make a program that can read data from a text file into memory.

    Here is the format of the text file:
    Quantity
    Brand
    Cost

    So text file 1 could be:
    2
    Dodge
    15000

    And text file 2 could be:
    2
    Dodge
    15000

    4
    Toyota
    6500

    I have created a struct called
    Code:
    struct Car
    {
    int quantity;
    char brand[20];
    double cost;
    };
    Now how I input data into the struct if I don't even know how big the struct array size should be?

    In my main I have Car Cars[]; declared but I have left the brackets empty because I don't know what the size it should be.

    Please help me with this.

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Why use an array if you don't know how many you're going to need? You should look into other containers, such as vector.

  3. #3
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    No need to use pointers at all.

    Create a std::vector<Car>. Open file. Read one Car from the file, and append it to the vector. Repeat (read another Car and append) until whole file read. Close file. Done.
    Right 98% of the time, and don't care about the other 3%.

    If I seem grumpy in reply to you, it is likely you deserve it. Suck it up, sunshine, and read this, this, and this before posting again.

  4. #4
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    Ah I see. Thank you so much!

  5. #5
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    Additionally, you shouldn't be using a char array here either; just use std::string for your brand name.
    Quote Originally Posted by anduril462 View Post
    Now, please, for the love of all things good and holy, think about what you're doing! Don't just run around willy-nilly, coding like a drunk two-year-old....
    Quote Originally Posted by quzah View Post
    ..... Just don't be surprised when I say you aren't using standard C anymore, and as such,are off in your own little universe that I will completely disregard.
    Warning: Some or all of my posted code may be non-standard and as such should not be used and in no case looked at.

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