What is the process for launching an external program with a time limit and receiving the standard output/error message and exit code in Rust?

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In Rust, you can use the std::process::Command struct to launch an external program. To specify a time limit, you can use the std::time::Duration struct to set a timeout period for the program to finish execution.

Here is an example of launching an external program with a time limit of 5 seconds:

use std::process::{Command, Stdio};
use std::time::Duration;
use std::io::ErrorKind;

fn main() {
    let mut child = Command::new("my_program")
                    .arg("argument1")
                    .arg("argument2")
                    .stdout(Stdio::piped())
                    .stderr(Stdio::piped())
                    .spawn()
                    .expect("failed to execute process");

    let timeout = Duration::from_secs(5); // Set a timeout of 5 seconds
    let result = child.wait_timeout(timeout).unwrap();

    match result {
        Some(status) => {
            if status.success() {
                // Program finished successfully
                let stdout = child.stdout.unwrap().into_string().unwrap();
                let stderr = child.stderr.unwrap().into_string().unwrap();
                println!("Standard output:\n{}", stdout);
                println!("Standard error:\n{}", stderr);
                println!("Exit code: {}", status.code().unwrap());
            } else {
                // Program failed to execute
                let stderr = child.stderr.unwrap().into_string().unwrap();
                println!("Error message:\n{}", stderr);
                println!("Exit code: {}", status.code().unwrap());
            }
        },
        None => {
            // Program timed out
            child.kill().expect("failed to kill process");
            let stderr = child.stderr.unwrap().into_string().unwrap();
            println!("Timed out after {} seconds. Error message:\n{}", timeout.as_secs(), stderr);
        }
    }
}

In this example, Command::new() is used to create a new command to launch the my_program executable with two arguments, argument1 and argument2. The stdout and stderr fields of the Command struct are set to Stdio::piped() so that we can capture the standard output and error of the program.

After starting the program with .spawn(), we wait for it to finish execution using child.wait_timeout(timeout), which waits for the program to exit for up to timeout duration. If the program exits within the timeout duration, wait_timeout() returns a Some(status) value, where status is the exit status of the child process. If the program takes longer than the timeout duration to exit, wait_timeout() returns None.

In the match statement, we check whether the program successfully exited by calling status.success(). If the program exited successfully, we can capture its standard output and error messages using .stdout.unwrap().into_string().unwrap() and .stderr.unwrap().into_string().unwrap(), respectively. We can also retrieve the program's exit code by calling status.code().unwrap(). If the program failed to execute successfully, we can retrieve its error message from its standard error output and exit code in a similar way.

If the program times out, we kill the child process using child.kill() to force it to exit. We can then retrieve the program's error message from its standard error output using child.stderr.unwrap().into_string().unwrap().