gajim-plural/src/command_system/implementation/execute.py

# Copyright (c) 2010, Alexander Cherniuk (ts33kr@gmail.com)
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"""
Provides facilities to safely execute expressions inside a shell process
and capture the resulting output, in an asynchronous fashion, avoiding
deadlocks. If the process execution time reaches the threshold - it is
forced to terminate. Consists of a tiny framework and a couple of
commands as a frontend.
"""

from subprocess import Popen, PIPE
from os.path import expanduser

from glib import timeout_add

from ..framework import CommandContainer, command, doc
from hosts import *

class Execute(CommandContainer):
    HOSTS = ChatCommands, PrivateChatCommands, GroupChatCommands

    DIRECTORY = "~"

    POLL_TIME = 100
    POLL_COUNT = 5

    @command("exec", raw=True)
    @doc(_("Execute expression inside a shell, show output"))
    def execute(self, expression):
        Execute.spawn(self, expression)

    @classmethod
    def spawn(cls, processor, expression):
        pipes = dict(stdout=PIPE, stderr=PIPE)
        directory = expanduser(cls.DIRECTORY)
        popen = Popen(expression, shell=True, cwd=directory, **pipes)
        cls.monitor(processor, popen)

    @classmethod
    def monitor(cls, processor, popen):
        poller = cls.poller(processor, popen)
        timeout_add(cls.POLL_TIME, poller.next)

    @classmethod
    def poller(cls, processor, popen):
        for x in xrange(cls.POLL_COUNT):
            yield cls.brush(processor, popen)
        cls.overdue(processor, popen)
        yield False

    @classmethod
    def brush(cls, processor, popen):
        if popen.poll() is not None:
            cls.terminated(processor, popen)
            return False
        return True

    @classmethod
    def terminated(cls, processor, popen):
        stdout, stderr = cls.fetch(popen)
        if stdout:
            processor.echo(stdout)
        elif stderr:
            processor.echo(stderr)

    @classmethod
    def overdue(cls, processor, popen):
        popen.terminate()

    @classmethod
    def fetch(cls, popen):
        data = popen.communicate()
        return map(cls.clean, data)

    @staticmethod
    def clean(text):
        strip = chr(10) + chr(32)
        return text.strip(strip)

class Show(Execute):

    @command("sh", raw=True)
    @doc(_("Execute expression inside a shell, send output"))
    def show(self, expression):
        Show.spawn(self, expression)

    @classmethod
    def terminated(cls, processor, popen):
        stdout, stderr = cls.fetch(popen)
        if stdout:
            processor.send(stdout)
        elif stderr:
            processor.send(stderr)