How to Conditionally Compile Code in Rust with cfg

Use the #[cfg(...)] attribute to conditionally include or exclude code based on build configuration. Place the attribute directly above the item you want to conditionally compile, such as a function or module.

#[cfg(target_os = "linux")]
fn linux_specific() {
    println!("Running on Linux");
}

#[cfg(not(target_os = "linux"))]
fn other_os() {
    println!("Running on something else");
}

To enable custom flags, pass --cfg to the compiler via RUSTFLAGS or define them in Cargo.toml under [profile.dev] or [profile.release].

Conditionally compiling code in Rust with cfg lets you include or exclude parts of your code depending on the environment, like the operating system or specific build settings. Think of it as a switch that turns certain code on or off before the program is even built, ensuring you only ship what is necessary for that specific target.