[蟒蛇菜谱] Python调用shell命令，获取返回值和返回信息

# -*- coding: utf-8 -*-
import os
import subprocess
import signal

class MockLogger(object):
    ‘‘‘模拟日志类。方便单元测试。‘‘‘
    def __init__(self):
        self.info = self.error = self.critical = self.debug

    def debug(self, msg):
        print "__LOGGER__:"+msg
        
class Shell(object):
    ‘‘‘完成Shell脚本的包装。
    run()为普通调用，会等待shell命令返回。
    run_background()为异步调用，会立刻返回，不等待shell命令完成
    异步调用时，可以使用get_status()查询状态，或使用wait()进入阻塞状态，
    等待shell执行完成。
    异步调用时，使用kill()强行停止脚本后，仍然需要使用wait()等待真正退出。
    TODO 未验证Shell命令含有超大结果输出时的情况。
    ‘‘‘
    def __init__(self, cmd):
        self.cmd = cmd  # cmd包括命令和参数
        self.ret_code = None
        self.ret_info = None
        self.err_info = None
        #使用时可替换为具体的logger
        self.logger = MockLogger() 
        
    def run_background(self):
        ‘‘‘以非阻塞方式执行shell命令（Popen的默认方式）。
        ‘‘‘
        self.logger.debug("run %s"%self.cmd)
        # Popen在要执行的命令不存在时会抛出OSError异常，但shell=True后，
        # shell会处理命令不存在的错误，因此没有了OSError异常，故不用处理
        self._process = subprocess.Popen(self.cmd, shell=True, 
                stdout=subprocess.PIPE, stderr=subprocess.PIPE) #非阻塞
        
    def run(self):
        ‘‘‘以阻塞方式执行shell命令。
        ‘‘‘
        self.run_background()
        self.wait()

    def wait(self):
        ‘‘‘等待shell执行完成。
        ‘‘‘
        self.logger.debug("waiting %s"%self.cmd)
        self.ret_info, self.err_info = self._process.communicate() #阻塞
        # returncode: A negative value -N indicates that the child was 
        # terminated by signal N
        self.ret_code = self._process.returncode
        self.logger.debug("waiting %s done. return code is %d"%(self.cmd, 
                            self.ret_code))

    def get_status(self):
        ‘‘‘获取脚本运行状态(RUNNING|FINISHED)
        ‘‘‘
        retcode = self._process.poll()
        if retcode == None:
            status = "RUNNING"
        else:
            status = "FINISHED"
        self.logger.debug("%s status is %s"%(self.cmd, status))
        return status

    # Python2.4的subprocess还没有send_signal,terminate,kill
    # 所以这里要山寨一把，2.7可直接用self._process的kill() 
    def send_signal(self, sig):
        self.logger.debug("send signal %s to %s"%(sig, self.cmd))
        os.kill(self._process.pid, sig)

    def terminate(self):
        self.send_signal(signal.SIGTERM)

    def kill(self):
        self.send_signal(signal.SIGKILL)

if __name__ == "__main__":
    ‘‘‘test code‘‘‘
    # 1. test normal
    sa = Shell(‘who‘)
    sa.run()
    print "return code:", sa.ret_code
    print "return info:", sa.ret_info
    
    # 2. test stderr
    sb = Shell(‘ls /export/dir_should_not_exists‘)
    sb.run()
    print "return code:", sb.ret_code
    print "return info:", sb.ret_info
    print "error info:", sb.err_info
    
    # 3. test background
    sc = Shell(‘sleep 2‘)
    sc.run_background()
    print ‘warmly hello from parent process‘
    print "return code:", sc.ret_code
    print "status:", sc.get_status()
    sc.wait()
    print "return code:", sc.ret_code
    print "return info:", sc.ret_info
    
    # 4. test kill
    import time
    sd = Shell(‘sleep 2‘)
    sd.run_background()
    time.sleep(1)
    sd.kill()
    sd.wait() # NOTE, still need to wait
    print sd.ret_code
    print sd.ret_info
    
    # 5. test multiple command and uncompleted command output
    se = Shell(‘pwd;sleep 1;pwd;pwd‘)
    se.run_background()
    time.sleep(1)
    se.kill()
    se.wait() # NOTE, still need to wait
    print se.ret_code
    print se.ret_info
    
    # 6. test wrong command
    sf = Shell(‘aaaaa‘)
    sf.run()
    print sf.ret_code
    print sf.ret_info
    print sf.err_info