Execing Processes in Rust

Here’s the translation of the Go code to Rust, with explanations in Markdown format suitable for Hugo:

In the previous example, we looked at spawning external processes. We do this when we need an external process accessible to a running Rust process. Sometimes we just want to completely replace the current Rust process with another (perhaps non-Rust) one. To do this, we’ll use Rust’s implementation of the classic exec function.

use std::process::Command;
use std::os::unix::process::CommandExt;

fn main() {
    // For our example we'll exec `ls`. Rust doesn't require an
    // absolute path to the binary we want to execute, so we can
    // use `ls` directly.
    let mut cmd = Command::new("ls");

    // We'll give `ls` a few common arguments. Note that we add
    // these arguments separately.
    cmd.arg("-a").arg("-l").arg("-h");

    // In Rust, we don't need to explicitly set the environment
    // variables. The child process will inherit the environment
    // of the parent process by default.

    // Here's the actual `exec` call. If this call is successful,
    // the execution of our process will end here and be replaced
    // by the `/bin/ls -a -l -h` process. If there is an error,
    // we'll get a return value.
    let error = cmd.exec();

    // If we reach here, it means the exec call failed
    eprintln!("Failed to execute process: {:?}", error);
}

When we run our program it is replaced by ls.

$ cargo run
total 16
drwxr-xr-x  4 user 136B Oct 3 16:29 .
drwxr-xr-x 91 user 3.0K Oct 3 12:50 ..
-rw-r--r--  1 user 1.3K Oct 3 16:28 main.rs

Note that Rust, like many other languages, does not offer a classic Unix fork function. Usually this isn’t an issue though, since spawning processes and exec’ing processes covers most use cases for fork. For more complex scenarios, Rust provides the std::process module which offers fine-grained control over process creation and management.

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Execing Processes in Rust