How do I find the path to the home directory for Linux?

From the home crate.

The definition of home_dir provided by the standard library is incorrect because it relies on the $HOME environment variable which has basically no meaning in Windows. This causes surprising situations where a Rust program will behave differently depending on whether it is run under a Unix emulation environment. Neither Cargo nor rustup use the standard libraries definition – instead they use the definition here.

There is discussion about bringing home_dir back into the standard library, but for now the home crate is probably your best option. It provides canonical definitions of home_dir, cargo_home, and rustup_home:

match home::home_dir() {
    Some(path) => println!("{}", path.display()),
    None => println!("Impossible to get your home dir!"),
}