Background
I am developing a reverse shell in rust. I am using a PTY in order to create the sense of interactivity.

The crate i’m using is called portable_pty.

Their documents are pretty scarce, and the examples they show do not include reading the output of a command.

/// Struct to handle interaction with the pseudo terminal
pub struct Pty {
    /// The pseudo terminal to interact with
    pty_pair : PtyPair,
    /// What shell is spawned inside the pseudo terminal
    shell_handle : Box<dyn Child + Sync + Send>
}

impl Pty {
    /// Create a new pty instance. ``shell_name`` represents the name or path of the shell you wish to spawn. 
    /// 
    /// This function can fail. When a terminal is spawned, errors can occur. The error will be gracefully sent back to the caller.
    pub fn try_new(shell_name : &str) -> Result<Self, Error> {
        let pty_system = native_pty_system();
        let pty_pair = pty_system.openpty(PtySize {
            rows: 24,
            cols: 80,
            pixel_width: 0,
            pixel_height: 0,
        })?;

        let program_shell = CommandBuilder::new(shell_name);
        let shell_handle: Box<dyn Child + Sync + Send> = pty_pair.slave.spawn_command(program_shell)?;

        Ok(Self {
            pty_pair,
            shell_handle
        })
    }
    /// Writes a new command to the pseudo terminal. It returns back the output as a Vec<u8>.
    pub fn exec(&mut self, input_buff : &str) -> Result<Vec<u8>, Error> {
        let pty_pair = &self.pty_pair;
        let mut pty_in = pty_pair.master.take_writer()?;
        let mut pty_out = pty_pair.master.try_clone_reader()?;
        writeln!(pty_in, "{}", input_buff)?;
        let mut output = [0u8;1024];
        pty_out.read(&mut output)?;
        println!("Output of {} : {}", input_buff, String::from_utf8(output.to_vec())?);
        /*
        Only output given: 

        Windows PowerShell
        Copyright (C) Microsoft Corporation. All rights reserved.

        Install the latest PowerShell for new features and improvements! https://aka.ms/PSWindows
         */
        Ok(output.to_vec())
    }
}

As shown, the only output given is the PowerShell splash screen. I doubt that the line where i print the output is executed, as the format is not shown. And not the output of the command that is supposed to be executed.