tempnam() - when does it get deleted?

This is a discussion on tempnam() - when does it get deleted? within the C++ Programming forums, part of the General Programming Boards category; I have a program that optionally allows the user to overwrite the input file (binary) with the output file (text). ...

  1. #1
    Jack of many languages Dino's Avatar
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    tempnam() - when does it get deleted?

    I have a program that optionally allows the user to overwrite the input file (binary) with the output file (text).

    When I detect the output file is the same name as the input file, I create a temporary file, via tempnam(NULL), and write the output to it.

    When finished writing, I close both the input file and output file, and then look to see if the original input file needs to be overlaid with the output file. If it does, I open the output file in ios::in mode and the input file in ios:ut mode and simply copy it over via in.read and out.write.

    However, every time I end up with zero bytes read, and thus zero written. When I do not go through the overlay process, the output file is fine and has the data it is supposed to. When I do go through the overlay process, my counters from the primary process tell me the same amount of data was written. I have verified the output file does contains data from the primary operation.

    Does anything in this process sound suspect?

    Thanks, Todd
    Last edited by Dino; 01-16-2008 at 07:37 AM.

  2. #2
    and the hat of wrongness Salem's Avatar
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    AFAIK, it only creates the temporary name, not the actual file.
    So removing the file is still down to you.

    http://www.cplusplus.com/reference/c...io/tmpnam.html
    See also the difference with tmpfile()
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
    Jack of many languages Dino's Avatar
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    I think I might know what the problem is. I've defined the output file as an ostream. Methinks it should be a fstream. I'll try that and report back.

    Todd

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