How to write to a file in C ? (Code Snippet)

C++文件写入使用ofstream类，需包含<fstream>头文件；默认覆盖写入，可加std::ios::app追加、std::ios::binary写二进制；应检查打开和写入状态，依赖RAII自动关闭。

To write to a file in C++, use the ofstream class from the <fstream> header. It works much like std::cout, but outputs to a file instead of the console.

Basic file writing with ofstream

Open a file for writing, check if it succeeded, then write data using <<. Always close the file or let it go out of scope (which closes it automatically).

// Example:

Writing formatted or binary data

For plain text, << is fine. For raw bytes (e.g., structs, images), use write():

• file.write(reinterpret_cast<const char*>(&data), sizeof(data));

• Make sure the file is opened in binary mode: std::ios::binary

Error handling best practices

Always verify operations — writing can fail (e.g., disk full, permission denied).

• Check file.good(), file.fail(), or !file after writes
• Use file.clear() to reset error flags if retrying
• Prefer RAII: declare ofstream inside a limited scope so it auto-closes

Basically just open, write, and trust the destructor — unless you need append, binary, or tight error control.

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