Why Does `std::fstream::open()` Throw a \'No Such File or Directory\' Error When Creating a File?

File Creation Issue with std::fstream

Question:

When utilizing std::fstream for file I/O, encountering an error message of "No such file or directory" while attempting to create a file if it doesn't already exist. Specifically, the below code snippet is causing the issue:

<code class="cpp">std::fstream my_stream;
my_stream.open("my_file_name", std::fstream::binary | std::fstream::in | std::fstream::out);
if (!my_stream)
    std::cout << "error" << strerror(errorno);</code>

How can this issue be resolved to ensure file creation when necessary?

Answer:

The fstream::open() function requires a non-existing file if std::fstream::in is specified in the mode argument. To resolve the issue, either remove std::fstream::in from the mode flags or add std::fstream::trunc alongside the existing flags.

<code class="cpp">// Remove std::fstream::in
std::fstream my_stream;
my_stream.open("my_file_name", std::fstream::binary | std::fstream::out);

// Add std::fstream::trunc
std::fstream my_stream;
my_stream.open("my_file_name", std::fstream::binary | std::fstream::in | std::fstream::out | std::fstream::trunc);</code>

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