使用Python的Pexpect模块执行SSH登陆
Pexpect 的使用范围很广，可以用来实现与 ssh, ftp , telnet 等程序的自动交互；可以用来自动复制软件安装包并在不同机器自动安装；还可以用来实现软件测试中与命令行交互的自动化。
下载安装：
download pexpect-2.3.tar.gz tar zxvf pexpect-2.3.tar.gz cd pexpect-2.3 python setup.py install (do this as root)
其实这个过程一点都不难，唯一的问题就是登陆之后终端尺寸的大小（我理解是buffer），因为Pexpect在代码里面有hardcode，把终端尺寸默认设成(24, 80)了。所以你连上后打开emacs会发现，emacs只占据了整个终端的一小部分。
# pexpect hard-codes the terminal size as (24,80) (rows,columns). # This causes problems because any line longer than 80 characters gets # completely overwrapped on the printed outptut (even though # internally the code runs fine). We reset this to 99 rows X 200 # columns (arbitrarily chosen), which should avoid problems in all # reasonable cases. c.setwinsize(24,80)
OK, 知道问题了我们可以开始解决，既然支持child.setwinsize()，那我们就想办法获取当前终端大小，并且在ssh目标主机之后设置终端大小。
# 获取窗口大小
def getwinsize():
"""This returns the window size of the child tty.
The return value is a tuple of (rows, cols).
"""
if 'TIOCGWINSZ' in dir(termios):
TIOCGWINSZ = termios.TIOCGWINSZ
else:
TIOCGWINSZ = 1074295912L # Assume
s = struct.pack('HHHH', 0, 0, 0, 0)
x = fcntl.ioctl(sys.stdout.fileno(), TIOCGWINSZ, s)
return struct.unpack('HHHH', x)[0:2]
＃ 设置大小
child.expect('-bash-baidu-ssl.*')
child.sendline('ssh ' + host)
winsize = getwinsize();
child.setwinsize(winsize[0], winsize[1])
OK, 一切正常。打开emacs，感觉很幸福，但连接后我发现连接之前终端窗口本来就很小，现在想把窗终窗口最大化，一试就杯具了，窗口的确最大化了，但是emacs所占区域仍旧没有变化，也就是说连接后的子窗口尺寸和当前窗口尺雨不匹配，Signal终于要派上用场了：
def sigwinch_passthrough (sig, data):
winsize = getwinsize()
global child
child.setwinsize(winsize[0],winsize[1])
最后监听事件：
signal.signal(signal.SIGWINCH, sigwinch_passthrough)
一切正常！
下面贴上所有代码：
#!/usr/bin/python
import sys
import time
import pexpect
import os
import struct
import fcntl
import termios
import signal
def sigwinch_passthrough (sig, data):
winsize = getwinsize()
global child
child.setwinsize(winsize[0],winsize[1])
def getwinsize():
"""This returns the window size of the child tty.
The return value is a tuple of (rows, cols).
"""
if 'TIOCGWINSZ' in dir(termios):
TIOCGWINSZ = termios.TIOCGWINSZ
else:
TIOCGWINSZ = 1074295912L # Assume
s = struct.pack('HHHH', 0, 0, 0, 0)
x = fcntl.ioctl(sys.stdout.fileno(), TIOCGWINSZ, s)
return struct.unpack('HHHH', x)[0:2]
if __name__ == '__main__':
user = 'username'
passwd = 'password'
host = 'example.com'
print 'ssh ' + user + '@' + host + ' ...'
time.sleep(1)
child = pexpect.spawn('ssh relay', env = {"TERM" : "xterm-256color"})
signal.signal(signal.SIGWINCH, sigwinch_passthrough)
if len(sys.argv) > 1:
child.expect("Enter PASSCODE:")
child.sendline("PIN-CODE" + sys.argv[1])
child.expect('-bash-baidu-ssl.*')
child.sendline('ssh ' + host)
winsize = getwinsize();
child.setwinsize(winsize[0], winsize[1])
child.expect('.*password:.*')
child.sendline(passwd)
child.interact()
pass