python子进程通信冻结

Question

我有以下挂起的python代码:

cmd = ["ssh", "-tt", "-vvv"] + self.common_args
cmd += [self.host]
cmd += ["cat > %s" % (out_path)]
p = subprocess.Popen(cmd, stdin=subprocess.PIPE,
                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
stdout, stderr = p.communicate(in_string)

它应该通过ssh将字符串(in_string)保存到远程文件中.

文件已正确保存,但随后进程挂起.如果我使用

cmd += ["echo"] instead of
cmd += ["cat > %s" % (out_path)]

这个过程没有挂起所以我很确定我误解了沟通认为流程退出的方式.

你知道怎么写这个命令所以"cat>文件"不能让沟通挂起吗？

Answer 1

-tt.communicate()选项分配 tty 来防止子进程在关闭时退出p.stdin（EOF被忽略）。这有效：

import pipes
from subprocess import Popen, PIPE

cmd = ["ssh", self.host, "cat > " + pipes.quote(out_path)] # no '-tt'
p = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE)
stdout, stderr = p.communicate(in_string)

您可以使用paramiko--纯Python ssh库，通过ssh将数据写入远程文件：

#!/usr/bin/env python
import os
import posixpath
import sys
from contextlib import closing

from paramiko import SSHConfig, SSHClient

hostname, out_path, in_string = sys.argv[1:] # get from command-line 

# load parameters to setup ssh connection
config = SSHConfig()
with open(os.path.expanduser('~/.ssh/config')) as config_file:
    config.parse(config_file)
d = config.lookup(hostname)

# connect
with closing(SSHClient()) as ssh:
    ssh.load_system_host_keys()
    ssh.connect(d['hostname'], username=d.get('user'))
    with closing(ssh.open_sftp()) as sftp:
        makedirs_exists_ok(sftp, posixpath.dirname(out_path))
        with sftp.open(out_path, 'wb') as remote_file:
            remote_file.write(in_string)

其中makedirs_exists_ok()函数模仿os.makedirs()：

from functools import partial
from stat import S_ISDIR

def isdir(ftp, path):
    try:
        return S_ISDIR(ftp.stat(path).st_mode)
    except EnvironmentError:
        return None

def makedirs_exists_ok(ftp, path):
    def exists_ok(mkdir, name):
        """Don't raise an error if name is already a directory."""
        try:
            mkdir(name)
        except EnvironmentError:
            if not isdir(ftp, name):
                raise

    # from os.makedirs()
    head, tail = posixpath.split(path)
    if not tail:
        assert path.endswith(posixpath.sep)
        head, tail = posixpath.split(head)

    if head and tail and not isdir(ftp, head):
        exists_ok(partial(makedirs_exists_ok, ftp), head)  # recursive call

    # do create directory
    assert isdir(ftp, head)
    exists_ok(ftp.mkdir, path)