C++ read doubles from a text file

Question

screenshot Hi guys I'm trying to read a text file that has 3 doubles in a row and then save these three values into my variables ( 1 variable per double).

So far my code is looking like this:

cout<<"ready to read file...:";
ifstream theFile("pose.txt");
double first,second,third;
while(theFile >> first >> second >> third){
    cout<<"In while loop and got following values: ";
    cout<< first<<endl<< second <<endl<< third;
}

And my input file looks like this when opened:

1.5 2.4 3.3

However even though the first cout runs and it tells me that the program is ready to read the file, it doesn't enter the while loop.

I've tried using other methods of reading the file which have also been ineffective.

Any help is welcome, Thanks.

Have you tried to step through the code line by line in a debugger? — Some programmer dude, Feb 27 '16 at 17:05
I posted my input file too, yeah I've tried debugging but I'm not sure exactly it seems to skip the start of the while loop. — Tomer Li-ran, Feb 27 '16 at 17:07
Post a [MCVE] please. What you have looks fine so far, your error is elsewhere. — πάντα ῥεῖ, Feb 27 '16 at 17:07
This code looks fine. @TomerLi-ran, you need to give more details since the error isn't here. — Akshay Arora, Feb 27 '16 at 17:11
What is your locale (language setting)? Maybe your system uses comma as the decimal separator? — Some programmer dude, Feb 27 '16 at 17:16
Hi all, I've edited my code so that you can see a screenshot of the way it looks on my IDE, i've changed it slightly and still it's not working. Thanks for the interest please look at it and tell me what you think! — Tomer Li-ran, Feb 27 '16 at 17:19
The screenshot clearly shows the "The file HAS NOT been opened correctly" message. File name wrong? Or in the wrong place? — BoBTFish, Feb 27 '16 at 17:19
The file name is correct and it should be in the right place as seen on the screenshot it is included in the project... — Tomer Li-ran, Feb 27 '16 at 17:25
Try to put absolute path to your input file or `./` before name of the file — segevara, Feb 27 '16 at 17:32
When you experience such a problem with `std::ifstream`, it's often easier to reproduce and analyse the problem with a `std::istringstream`. It has also the big advantage that you can create a true MCVE and post it here, and we can just do a one-step copy & paste to test it ourselves. — Christian Hackl, Feb 27 '16 at 18:15

score 0 · Answer 1 · edited May 23 '17 at 12:16

0

I found the answer on another question on StackOverflow. This is the link to the answer: https://stackoverflow.com/a/23448835/4117002

Basically I had to specify in Xcode the path of the text file, even though I had already created it in the project.

Thanks for the help anyway everyone!

edited May 23 '17 at 12:16

Community

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answered Feb 27 '16 at 17:42

Tomer Li-ran

11
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score 0 · Answer 2 · answered Feb 27 '16 at 17:51

I don't recognize your IDE from the screenshot but if it is like other IDEs, your program will not by default be run in the directory containing your source file main.cpp and your data file example.txt. It will be run in a directory configured in the project settings, probably the one where the executable is created.

So let's pretend the (debug build) executable is created in Products/Debug and is run there. In that case:

std::ifstream theFile("example.txt");

will fail because there is no file called example.txt in Products/Debug. You would need to open theFile with the relative path:

std::ifstream theFile("../../InputFileExample/example.txt");

or else specify the absolute filename.

score 0 · Answer 3 · edited Apr 20 '16 at 15:01

0

Assuming you are familiar with cpp:

Buffer each line of ifstream data into a std::string. Example:
```
std::getline(std::ifstream , std::string )
```
Buffer the std::string into std::istringstream. Example:
```
std::istringstream (std::string )
```
Split std::istringstream into the double values you need. Example:
```
istringstream iss
```

iss >> first >> second >> third

Good Luck!

edited Apr 20 '16 at 15:01

Benjamin W.

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answered Apr 20 '16 at 14:42

Rishi Alluri

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C++ read doubles from a text file

3 Answers3