Reading external files, (not!!)

This is a discussion on Reading external files, (not!!) within the C++ Programming forums, part of the General Programming Boards category; Hello all, I am a complete newbie trying to learn this stuff. I actually have two questions; 1) I have ...

  1. #1
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    Question Reading external files, (not!!)

    Hello all,

    I am a complete newbie trying to learn this stuff. I actually have two questions;

    1) I have been looking through a few of the recent threads and I have noticed some differences to my programming, (I'm using MicroSoft Visual Studio 6.0 by the way).

    On this site's programs the header files are:-
    Code:
    #include <iostream>
    #include <fstream>
    On my programming I have to add .h to the header files. Why?

    I'll post the second question on a different message.

  2. #2
    Just a Member ammar's Avatar
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    You should use <iostream> and <fstream> without any .h, because it's the standard library, try using them and adding this line:
    Code:
    using namespace std;
    and it will work fine!

    Note:
    There are many threads dealing with this subject in more details, you might want to check them out!
    none...

  3. #3
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    Question Reading external files (not!!) Part 2.

    I apologise for blathering on but I am really stuck on this problem.

    I have an external file called "test.dat" from a write program. This bit actually works and the following code is supposed to read from it, but it doesn't. Why, please???

    Code:
    #include <iostream.h>
    #include <fstream.h>
    #include <stdlib.h>
    
    const int max = 80;
    
    int main ()
    {
    ifstream input_file;
    char film[max];
    
    input_file.open("test.dat",ios::in|ios::nocreate);
    
    if (input_file.fail())
    {
    cout << "File does not already exist." << endl;
    exit(1);
    }
    
    while (input_file.peek() != EOF)
    {
    input_file.getline (film, max);
    cout << film <<endl;
    }
    cout << endl;
    
    input_file.close();
    return 0;
    }
    The program compiles OK but when it runs, the result is
    "File does not already exist."

    I am frustrated and confused.

  4. #4
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    Thanks very much. I'll try that.

  5. #5
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    Thanks ammar.

    I tried that but got 2 probs.

    1. The compiler didn't recognise <stdlib>
    2. When I deleted <stdlib> the compiler didn't recognise
    ios::nocreate. It viewed it as an identifier.

    Sorry fella, I am a REAL newbie here!

  6. #6
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    Salem,

    if you read my reply to Ammar, you know I'm new to this.

    What's "Threads merged" mean?

    I tried adding the test.dat file to the project thinking that it would then be in the right directory. Still the same problem.

  7. #7
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    If you put the data file in the project folder, then you can use just the file name, otherwise use the complete path to your data file with double back slashes:

    ifstream inFile("C:\\DataFolder\\test_data.txt")

  8. #8
    Pursuing knowledge confuted's Avatar
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    Threads merged means that he took the two threads (posts/messages) that you had on this board about similar topics and put them both together under one heading. It has nothing to do with programming, it's just Salem flexing his powers as a mod
    Away.

  9. #9
    C++ Developer XSquared's Avatar
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    The ios namespace isn't part of the most recent standard. You should use ios_base::in instead. nocreate was removed from the newest standard, too.

    Oh, and if you remove the .h from a standard C library, add c to the front (<stdio.h> becomes <cstdio>).
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

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  10. #10
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    Originally posted by 7stud
    If you put the data file in the project folder, then you can use just the file name, otherwise use the complete path to your data file with double back slashes:

    ifstream inFile("C:\\DataFolder\\test_data.txt")
    Hi 7stud.

    Thanks for your reply. I tried it but got the same old result---

    "File does not already exist."

    Getting a bit fed up, failing at the first hurdle!!

  11. #11
    Registered User major_small's Avatar
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    Originally posted by ammar
    You should use <iostream> and <fstream> without any .h, because it's the standard library, try using them and adding this line:
    Code:
    using namespace std;
    and it will work fine!

    Note:
    There are many threads dealing with this subject in more details, you might want to check them out!
    that doesn't work with all compilers... i use borland v. 4.5, and i need to use the .h files because it doesn't have the newer libraries...
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  12. #12
    Code Goddess Prelude's Avatar
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    >i use borland v. 4.5, and i need to use the .h files because it doesn't have the newer libraries...
    Get a newer compiler. You're missing out on a lot of new features and there are free compilers for download that comform fairly well to the standard. You should only be using an older compiler to maintain legacy code that won't compile with a newer compiler for some reason.
    My best code is written with the delete key.

  13. #13
    C++ Developer XSquared's Avatar
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    For example, Dev-C++.
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

    You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie

  14. #14
    Registered User major_small's Avatar
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    i will one day... but I dont' feel like getting my dad's permission to d/l anything (he's the computer nazi and thinks broadband and file-sharing is evil)... eh... i have no problems writing my programs with this one... for now... and the class i'm taking is using this one... i actually have visual studio, but i haven't installed it yet...
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  15. #15
    Code Goddess Prelude's Avatar
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    >i actually have visual studio
    That really isn't much better. I never use Visual Studio for C++, it's just too much of a headache.
    My best code is written with the delete key.

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