Send command and exit using python pty pseudo term

Question

Using python pty module, i want to send some commands to the terminal emulator, using a function as stdin (as pty module wants), and then force quitting. I thought about something like

import pty
cmnds = ['exit\n', 'ls -al\n']
# Command to send. I try exiting as last command, but it doesn't works.

def r(fd):
    if cmnds:
        cmnds.pop()
        # It seems is not executing sent commands ('ls -al\n')
    else:
        # Can i quit here? Can i return EOF?
        pass

pty.spawn('/bin/sh', r)

Thank you

Answer 1

Firstly, the pty module does not allow you to communicate with the terminal emulator Python is running in. Instead, it allows Python to pretend to be a terminal emulator.

Looking at the source-code of pty.spawn(), it looks like it is designed to let a spawned process take over Python's stdin and stdout while it runs, which is not what you want.

If you just want to spawn a shell, send commands to it, and read the output, you probably want Python's subprocess module (in particular, if there's just one command you want to run, the subprocess.Popen class' .communicate() method will be helpful).

If you really, really need the sub-process to be running in a pty instead of a pipe, you can use os.openpty() to allocate a master and a slave file descriptor. Use the slave file descriptor as the subprocess' stdin and stdout, then write your commands to the master file descriptor and read the responses back from it.