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c++c++11exceptionfilestreamstd

Are Exceptions Thrown when 'std::fstream' Fails to Open?

Is there a way to get the fstream to throw an exception when it fails to open a file, and how would I do this?

I know about the std::fstream.exceptions() method and how to assign bits to it, but what 'bit' would throw the exception?

Solution

  • Iostreams can be any of three different failure states: fail, bad, and eof. The documentation shows you clearly how to cause any one of those to throw an exception; by default, none of them do, but evaluating a stream object in a boolean context returns false if any of the failure modes have occured.

    Example:

    #include <fstream>

std::ifstream infile;
infile.expections(std::ios::failbit);
infile.open("foo.txt");    // throws on failure