文件流无法打开

Question

I have the following C++ code as part of a larger program:

/* Open the output streams */
    std::ofstream outputFile;
    outputFile.open(outputName);
    std::ofstream outputFile1;
    outputFile1.open(outputName1);
    std::ofstream outputFile2;
    outputFile2.open(outputName2);

    std::cout <<  outputFile.is_open() << " " << outputFile1.is_open() << " " << outputFile2.is_open() << std::endl;
if (inputFile.is_open() && outputFile.is_open() && outputFile1.is_open() && 

outputFile2.is_open())
...

It's supposed to open several output file streams which will then - if they are all open - do a series of operations which writes to each one. However the program terminates early because the streams are never open:

0 0 0
Filestream or output streams could not open, ending program!

The variables outputName are std::strings, which I thought was allowed in C++11 (I have the -std flag enabled for C++11 in my OpenBlocks compiler options).

I'm not sure why the streams won't open.

Thanks.

Answer 1

File streams could fail to open for a number of reasons, such as if the path is invalid, if access is denied, or if the file is already open for writing in another program.

These errors are OS-dependent, and thus there is no standard way of reporting which one occured. However, you may be able to obtain an error code with the answers to this question .

If you're using Windows, be careful; if reports error code 5 (access denied) for all sorts of reasons that have nothing to do with permissions.