file io with dev c++

[7stud]

I can't seem to get it to work. I've tried using the full path name, as well as putting the file in the same directory as the dev c++ folder, but I am unable to open the file. Here's my code:

#include <iostream>
#include <fstream>
using namespace std;
      
int main()
{
    ifstream inFile("C:\\Documents and Settings\\user 3\\My Documents\\TestData\\data.txt");
    if(!inFile)
    {
        cout<<"error opening file"<<endl;
    }
    
    system("PAUSE");
    return 0;
}

[Slacker]

Do you know why the file can't be opened? Sometimes it's more informative to get some internal error messages going rather than your own:

#include <fstream>
#include <cstdio>
#include <cstdlib>

int main()
{
  std::ifstream fin ( "C:\\Documents and Settings\\user 3\\My Documents\\TestData\\data.txt" );

  if ( !fin ) std::perror ( 0 );

  std::system ( "PAUSE" );
}

A good idea for any IDE is to find out exactly where the files are expected. I usually forget and end up opening a file for writing, then go find it to see where I should put my files for reading. Spaces in the path and/or directory names over 8 characters also seem to be an issue with Windows, so you may need to remove them with that tilde thingie:

std::ifstream fin ( "C:\\docume~1\\user 3\\mydocu~1\\TestData\\data.txt" );

[7stud]

Thanks for the response.

A good idea for any IDE is to find out exactly where the files are expected. I usually forget and end up opening a file for writing, then go find it to see where I should put my files for reading.

That worked. I found the written file in:

C:\Dev-Cpp\c++ programs

I can also read files put in that directory. Can't dev c++ read files in other directories?

[prog-bman]

Dev-C++ is not a compiler it is an IDE. It uses Mingw(GCC). And yes it can read files from any directory.

[major_small]

I can also read files put in that directory. Can't dev c++ read files in other directories?

what makes you think it's Dev-C++? try taking the binary you create out of that directory, and put it somewhere else... what happens to your file I/O now?

you should attempt to use relative file paths whenever possible, and make sure the end user knows not to mess with the file structure you build around your program. Or if they do, have some way they can tell your program how they changed it.

by relative file paths, I mean like this: say you have your program in a folder called myprog. in myprog is your program (myprog.exe) and your data files all neatly tucked away in a folder (called data).

so this is how it looks:

+ myprog
|
+--myprog.exe
|
+--+data
     +--file1.dat
     +--file2.dat

your program would try to open up "data/file1.dat". Now imagine that you have the same file structure, except your program is in a folder called bin. you'd access those by opening "../data/file1.dat". That's telling your program to go up one directory, go down into data, and file file1.dat.

note those are linux file paths... for windows, just use \\ in place of all the /'s


edit: another key component I just remembered: The directory holding your binary won't always be the directory your binary is run in... for example, if you write a script to run a binary in another directory, depending on your setup, the binary won't run in the directory it's sitting in, but in the directory the script that called it is in.