How to pipe commands in rust?

I am trying to execute a command in a shell and get the return value as a string. The command I'm trying to execute is ps axww | grep mongod | grep -v grep.

I've seen solutions over the internet, but they don't explain the code, so it is hard customising it to my needs.

example: how to do a sandwich pipe in rust? & Pipe between two child processes

Can someone please provide a solution and go line by line explaining how it works in layman's terms.

What you need is the documentation, where they do explain everything line by line, with thorough examples. Adapted from it, here is your code

use std::process::{Command, Stdio};
use std::str;

fn main() {
    let ps_child = Command::new("ps") // `ps` command...
        .arg("axww")                  // with argument `axww`...
        .stdout(Stdio::piped())       // of which we will pipe the output.
        .spawn()                      // Once configured, we actually
                                      // spawn the command...
        .unwrap();                    // and assert everything went right.
    let grep_child_one = Command::new("grep")
        .arg("mongod")
        .stdin(Stdio::from(ps_child.stdout.unwrap())) // Pipe through.
        .stdout(Stdio::piped())
        .spawn()
        .unwrap();
    let grep_child_two = Command::new("grep")
        .arg("-v")
        .arg("grep")
        .stdin(Stdio::from(grep_child_one.stdout.unwrap()))
        .stdout(Stdio::piped())
        .spawn()
        .unwrap();
    let output = grep_child_two.wait_with_output().unwrap();
    let result = str::from_utf8(&output.stdout).unwrap();
    println!("{}", result);
}

See the playground (which of course won't output anything since there is no process called mongod running...).