Interacting with bash from python

问题:

I've been playing around with Python's subprocess module and I wanted to do an "interactive session" with bash from python. I want to be able to read bash output/write commands from Python just like I do on a terminal emulator. I guess a code example explains it better:

>>> proc = subprocess.Popen(['/bin/bash'])
>>> proc.communicate()
('user@machine:~/','')
>>> proc.communicate('ls\n')
('file1 file2 file3','')

(obviously, it doesn't work that way.) Is something like this possible, and how?

Thanks a lot

回答1:

Try with this example:

import subprocess

proc = subprocess.Popen(['/bin/bash'], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
stdout = proc.communicate('ls -lash')

print stdout

You have to read more about stdin, stdout and stderr. This looks like good lecture: http://www.doughellmann.com/PyMOTW/subprocess/

EDIT:

Another example:

>>> process = subprocess.Popen(['/bin/bash'], shell=False, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
>>> process.stdin.write('echo it works!\n')
>>> process.stdout.readline()
'it works!\n'
>>> process.stdin.write('date\n')
>>> process.stdout.readline()
'wto, 13 mar 2012, 17:25:35 CET\n'
>>> 

回答2:

pexpect is designed specifically for this kind of task. It's pure Python and it's inspired by expect, the venerable TCL tool.

回答3:

An interactive bash process expects to be interacting with a tty. To create a pseudo-terminal, use os.openpty(). This will return a slave_fd file descriptor that you can use to open files for stdin, stdout, and stderr. You can then write to and read from master_fd to interact with your process. Note that if you're doing even mildly complex interaction, you'll also want to use the select module to make sure that you don't deadlock.

回答4:

I wrote a module to facilitate the interaction between *nix shell and python.

def execute(cmd):
if not _DEBUG_MODE:
    ## Use bash; the default is sh
    print 'Output of command ' + cmd + ' :'
    subprocess.call(cmd, shell=True, executable='/bin/bash')
    print ''
else:
    print 'The command is ' + cmd
    print ''

Check out the whole stuff at github: https://github.com/jerryzhujian9/ez.py/blob/master/ez/easyshell.py

回答5:

Use this example in my other answer: https://stackoverflow.com/a/43012138/3555925

You can get more details in that answer.

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import os
import sys
import select
import termios
import tty
import pty
from subprocess import Popen

command = 'bash'
# command = 'docker run -it --rm centos /bin/bash'.split()

# save original tty setting then set it to raw mode
old_tty = termios.tcgetattr(sys.stdin)
tty.setraw(sys.stdin.fileno())

# open pseudo-terminal to interact with subprocess
master_fd, slave_fd = pty.openpty()

# use os.setsid() make it run in a new process group, or bash job control will not be enabled
p = Popen(command,
          preexec_fn=os.setsid,
          stdin=slave_fd,
          stdout=slave_fd,
          stderr=slave_fd,
          universal_newlines=True)

while p.poll() is None:
    r, w, e = select.select([sys.stdin, master_fd], [], [])
    if sys.stdin in r:
        d = os.read(sys.stdin.fileno(), 10240)
        os.write(master_fd, d)
    elif master_fd in r:
        o = os.read(master_fd, 10240)
        if o:
            os.write(sys.stdout.fileno(), o)

# restore tty settings back
termios.tcsetattr(sys.stdin, termios.TCSADRAIN, old_tty)