File I/O with std::fs for reading and writing files

Rust's std::fs module provides file I/O. fs::read_to_string() reads a file into a String, fs::write() writes bytes. For larger files or streaming, use File::open() and BufReader/BufWriter for buffered I/O. Always handle errors with Result and ?. For paths, use std::path::Path for manipulation. I use fs::read_to_string() for small config files and BufReader for large logs. The API is straightforward but requires explicit error handling, which prevents silent failures. For async I/O, tokio::fs provides async equivalents. File I/O is a common source of errors (permissions, missing files), so robust error handling is critical.