spawn类
spawn是pexpect的主要类接口，功能是启动和控制子应用程序。
class pexpect.spawn(
command,args=[],
timeout=30,
maxread=2000,# pexpect从终端控制台一次读取的最大字节数
searchwindowsize=None,# 参数为匹配缓冲区字符串的位置，默认是从开始位置匹配
logfile=None,
cwd=None,
env=None,
ignore_sighup=True)其中command参数可以是任意已知的系统命令，比如：
child = pexpect.spawn('/usr/bin/ftp')
child = pexpect.spawn('/usr/bin/ssh user@example.com')
child = pexpect.spawn('ls -latr /tmp')当子程序需要参数时，还可以使用python列表来代替参数项：
child = pexpect.spawn('/usr/bin/ftp',[])
child = pexpect.spawn('/usr/bin/ssh' ,['user@example.com'])
child = pexpect.spawn('ls', ['-latr', '/tmp'])注意的是，pexpect不会解析shell命令中的元字符，包括重定向‘>’、管道‘|’或者‘*’，当然我没有可以通过将这三个特殊元字符的命令作为/bin/bash 的参数进行调用，例如
child = pexpect.spawn('/bin/bash -c "ls -l|grep LOG >logs.txt"')
child.expect(pexpect.EOF)或者
shell_cmd = 'ls -l |grep LOG>logs.txt'
child = pexpect.spawn('/bin/bash',['-c',shell_cmd]
child.expect(pexpect.EOF)pexpect提供了2种途径写入log，一种为写到日志文件，另一种是标准输出。
写入日志文件：
child = pexpect.spawn('some_command')
fout = file('mylog.txt','w')
child.logfile = fout
输出控制台：
child = pexpect.spawn('some_command')
child.logfile = sys.stdout实例：
"""
This runs a command on a remote host using SSH. At the prompts enter hostname,
user, password and the command.
"""
import pexpect
import getpass, os
#user: ssh 主机的用户名
#host：ssh 主机的域名
#password：ssh 主机的密码
#command：即将在远端 ssh 主机上运行的命令
def ssh_command (user, host, password, command):
"""
This runs a command on the remote host. This could also be done with the
pxssh class, but this demonstrates what that class does at a simpler level.
This returns a pexpect.spawn object. This handles the case when you try to
connect to a new host and ssh asks you if you want to accept the public key
fingerprint and continue connecting.
"""
ssh_newkey = 'Are you sure you want to continue connecting'
# 为 ssh 命令生成一个 spawn 类的子程序对象.
child = pexpect.spawn('ssh -l %s %s %s'%(user, host, command))
i = child.expect([pexpect.TIMEOUT, ssh_newkey, 'password: '])
# 如果登录超时，打印出错信息，并退出.
if i == 0: # Timeout
print 'ERROR!'
print 'SSH could not login. Here is what SSH said:'
print child.before, child.after
return None
# 如果 ssh 没有 public key，接受它.
if i == 1: # SSH does not have the public key. Just accept it.
child.sendline ('yes')
child.expect ('password: ')
i = child.expect([pexpect.TIMEOUT, 'password: '])
if i == 0: # Timeout
print 'ERROR!'
print 'SSH could not login. Here is what SSH said:'
print child.before, child.after
return None
# 输入密码.
child.sendline(password)
return child
def main ():
# 获得用户指定 ssh 主机域名.
host = raw_input('Hostname: ')
# 获得用户指定 ssh 主机用户名.
user = raw_input('User: ')
# 获得用户指定 ssh 主机密码.
password = getpass.getpass()
# 获得用户指定 ssh 主机上即将运行的命令.
command = raw_input('Enter the command: ')
child = ssh_command (user, host, password, command)
# 匹配 pexpect.EOF
child.expect(pexpect.EOF)
# 输出命令结果.
print child.before
if __name__ == '__main__':
try:
main()
except Exception, e:
print str(e)
traceback.print_exc()
os._exit(1)Last updated