Create temporary file in C++

Question

I need to create a temporary file, fill it with some data and send the result to a function that accepts only std::istreams.

I tried using tmpfile() and it works for my first requirement - 'create a file and fill it with some data', but it returns a FILE* and there is no way to convert it (as far as I know) to std::streams.

Is there a C++ way of creating a temporary file? If this is not possible, how reliable is tmpnam to return a valid file name? Did anyone test this on Android or iOS?

EDIT: I don't want to copy the data to std::stringstream as a part of my test is reading the data from the disk.

"*send the result to a function that accepts only std::istreams.*" Not a file, but: Do you know istringstream? — deviantfan, Sep 25 '14 at 20:35
I don't want to copy the data. A part of my tests is reading from disk... — Mircea Ispas, Sep 25 '14 at 20:37
Is there any particular reason you believe that `tmpnam` won't do what you want? — Mats Petersson, Sep 25 '14 at 20:39
@MatsPetersson No. The only reason I prefer to create a temp file is to avoid adding the code to delete it after I'm done with the tests — Mircea Ispas, Sep 25 '14 at 20:58

score 2 · Accepted Answer · answered Sep 25 '14 at 21:00

2

If you want an alternative to std::tmpfile or std::tmpnam, you might want to look at the Boost Filesystem library. It contains a function unique_path() that will give you a place to put directories, files, etc.

It also includes other filesystem manipulation features that the standard library doesn't have, like iterating over files in a directory. I've found these especially useful for unit tests.

answered Sep 25 '14 at 21:00

Steve

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one should note that the use of boost::filesystem::unique_path() is discouraged, as is the use of the original C library calls: it poses a security risk. This is addressed in https://stackoverflow.com/questions/43316527/what-is-the-c17-equivalent-to-boostfilesystemunique-path -- in the end the way to handle these is to use calls that generate a filename and open it atomically, returning an open file pointer. – markgalassi Apr 17 '21 at 05:34

Create temporary file in C++

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