I have a program that I'm attempting to write various files to. In an attempt to clean it up I would like to put these files into a directory. My program is running in a directory different from the sln for VS 2012 i.e. the exe is the only part of the VS files in the directory. If I simply print the files, it's fine but if I attempt to print those same files to a different directory, then it doesn't do anything. I printed out the directory that I'm attempting to access and I'm getting "000000" as a response. code looks like:
std::ofstream output
output.open("\myFiles\entityOutput.csv", std::ios::app);
output << "print some stuff here" << std::endl;
I'm sure it's something simple but I haven't been able to figure out what. Tried "\\myFiles....." already "/myFiles" etc. I'm on a Windows 7 system as well.
That's because, while opening a file, you need to swap \ with either \\ or /. The reason is that \ character is considered as a special one that's used for example to represent end of line character (\n).
Just swap output.open("\myFiles\entityOutput.csv", std::ios::app);
to output.open("/myFiles/entityOutput.csv", std::ios::app);,
however make sure that the path is also correct!
Usually it's a good programming practice to check whether or not a file opening succeeded at first.
Related
I'm trying to open a file where my program runs, I could open a file in directories like this:
myfile.open("D:\\users.txt");
But I want to open this file:
myfile.open("users.txt");
users.txt is placed where my program is.
users.txt is placed where my program is.
The current working directory of your process may not be where your program executable is. The two are not bound together.
This:
myfile.open("users.txt");
should work just fine. However, I have encountered situations where the program could not read the file. That was due to the white spaces being included within the full path:
eg: "C:\Folder1\Folder 2\file.txt"
Make sure you don't have any white spaces there...
I recommend reading up on Naming Files, Paths, and Namespaces to give you a better understanding how Win32 API handles File paths, and also Namespaces. It will help you in the long run when you need to open USB and Serial connections to external devices.
I've got a program that is going to have several resource files that the user can put somewhere on the computer that isn't in the same folder as the executable. How do I get open those files?
I've found lots of answers saying that the reason things aren't working is that the file isn't in the working directory. I've tried providing fully qualified paths:
ifstream str;
str.open("/home/millere/foo.txt")
but that was unsuccessful. I know the path was correct (copy and paste). I can't find any documentation on it, but I assume it has to be possible. (vim ~/foo.txt from anywhere other than ~ works, for example).
Assuming you meant to use ifstream instead of iostream, your code is correct. ifstream can use a path to a file as well as the name of a file in the working directory.
No exceptions are thrown if the file does not exist, but the fail bit is set. You should check for this before trying to do anything with the stream.
std::ifstream input("/home/bob/stuff.txt");
if (!input) std::cerr << "Could not open the file!" << std::endl;
else
{
// ...
}
If you still cannot extract data from the file, the problem is somewhere else in your code.
I had the same issue and quickly noticed that, open when trying to get from a difference folder, had a different source directory (if using Cmake, the one that was specified by the cmake). You can find out, what the ouput/input source directory is by doing
system("ls")
or
system("dir")
on windows to show the content of the current ouput/input directory.
I am have a trouble in using fopen() with relative path. I wanted to use fopen like this:
fopen("\\Saurabh\\pqrs.txt");
i am getting filePointer as null.
The situation arose because I am trying to create a setup or deployment project which has to read files. The file paths chosen by default after user executes setup are C:\Program Files\Setup..
(where exe is dumped). So I dumped the files in the same folder and gave path(fixed path or hardcoded) to those files in the program.
If the user selects some other path for installation, the program fails.
Is there any way I can fix this?
Two problems:
You need to escape the backslash character. Write \\.
You need to use a relative path. By starting a path with \\ you mean start from the root directory.
Putting these together, I think you should write:
fopen("Saurabh\\pqrs.txt");
Make sure you double up the \ characters. The string you're passing in should be "Saurabh\\pqrs.txt". Note that beginning a path with \\ means that it's not relative. (Well, actually it's relative to your current drive, but I doubt that's what you're looking for.)
I am working on figuring out how to use Xcode 4 to debug c++ projects.
I have basically copy pasted a working c++ executable that when compiled from the terminal ran fine.
However, i was thinking it might be nice to use Xcode for debugging. So I am trying to migrate the single .cpp file into Xcode as a command line tool.
I need to read in a file called numbers.txt (which I supply through a command line argument) which is located in my project directory, and then out put to a file (whose name I also specify as an argument.)
The problem I am running into is that the files that are supplied as command line arguments are failing to open.
ifstream in;
ofstream out;
in.open(argv[1]);
out.open(argv[2]);
I have checked to make sure that the arguments are being properly passed and are named correctly. The ifstream in is being supplied with `numbers.txt', which I want to open a text file that I already have.
However when I check to make sure the ifstream is open:
if(in.is_open() == false){
cerr << "Unable to open input file" << endl;
return 1;
}
I get the error.
I suspect this has something to do with how Xcode organizes the project.
my numbers.txt file is just sitting in the Xcode project folder, and I have only one .cpp class and one product, the executable.
anyone know what I am missing here?
The executable built by Xcode is in a different folder than the project. Passing in the name of the file without an absolute path before it will cause the executable to look for it in the wrong place, which is why it can't be found. Some of the possible solutions are to include the file as part of the build process (so it ends up in the same directory as the executable) or to pass the file to be opened by its absolute path. There are other ways to solve the problem, too, but hopefully that should be enough to get you started.
Old thread, but i have faced the same problem now, and it is easy to solve. Just copy the file in the build phase.
Here is an screenshot of the final result (note the destination, subpath and checkbox):
alt text http://img638.imageshack.us/img638/5731/screenshot20100613at121.png
Why does the c++ program produce the error shown? I'm especially confused since outfile opens without error yet infile displays the error? Both are defined in xcode exactly the same!! I've altering the "path type" setting without success. The open on infile always fails! Any suggestions would be very much appreciated!!
For those who responded thanks but as you can see but infile and outfile exist and are in the same location:
alt text http://img709.imageshack.us/img709/9316/screenshot20100613at123.png
In Xcode, expand the "Targets" node and find your target. Given what I've seen, it'll be the only one there.
Next, right-click on your project and add a new "Copy Files" build phase. When the dialog box comes up, make sure you set the Destination to "Products Directory".
The new build phase will appear beneath your target with whatever name you gave it. Drag your in_file and out_file there.
Compile and run.
In your current case out_file would be created even if it doesn't exist (because you're using std::ofstream).
in_file, on the other hand, has to exist, and (I guess there is no such file in the directory with created binary), hence an error is produced.
Did you try launching your compiled application with the file in the same folder where the binary file is?
Probably there is no file named "in_file" in the program's working directory, so it can't be opened for reading.
For outfile this doesn't matter since it is opened for writing and if it doesn't exist yet it will just be created.
The directory listing you posted doesn't show where the compiled executable is, but probably it will be somewhere in the build directory. Probably this is then also its working directory and the place where the input file would need to be. (Look for the out_file the program creates when it is run, it will be created in the working directory, the same directory where it searches for in_file. And it is not the directory you posted the listing of, the out_file there is too old.)
Turns out you have to specifically create the file here:
Project Path/build/Debug
apparently you can't just define it directly in the xcode project