Python之子进程subprocess模块
http://www.cnblogs.com/vamei/archive/2012/09/23/2698014.html
http://blog.csdn.net/jgood/article/details/4498166
http://docs.python.org/library/subprocess
subprocess.call()
[root@typhoeus79 20130925]# more test.py #!/usr/bin/env python2.7 #-*- coding:utf8 -*- import subprocess rc = subprocess.call(["ls","-l"]) print "rc = ",rc [root@typhoeus79 20130925]# ./test.py total 4 -rwxr-xr-x 1 root root 118 Sep 25 11:18 test.py rc = 0
将程序名ls和其对应的参数放在一个list中传给subprocess.call()
通过一个shell来解释字符串
[root@typhoeus79 20130925]# ./sub_shell.py total 4 -rwxr-xr-x 1 root root 125 Sep 25 11:22 sub_shell.py rc = 0 [root@typhoeus79 20130925]# more sub_shell.py #!/usr/bin/env python2.7 #-*- coding:utf8 -*- import subprocess rc = subprocess.call("ls -l",shell=True) print "rc = ",rc
使用shell=True这个参数,使用字符串而不是使用list来运行子进程。python先运行一个shell,然后这个shell来解释整个字符串
Popen
基于Popen()的封装(wrapper),这些封装的目的在于让我们容易使用子进程。当我们想要更个性化我们的需求的时候,就要转向Popen类,该类生成的对象用来代表子进程
Using the subprocess module =========================== This module defines one class called Popen: class Popen(args, bufsize=0, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=False, shell=False, cwd=None, env=None, universal_newlines=False, startupinfo=None, creationflags=0):
[root@typhoeus79 20130925]# ./sub_popen.py parent process <subprocess.Popen object at 0x7fed17542050> [root@typhoeus79 20130925]# PING www.a.shifen.com (220.181.111.148) 56(84) bytes of data. --- www.a.shifen.com ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 4002ms [root@typhoeus79 20130925]# more sub_popen.py #!/usr/bin/env python26 #-*- coding:utf8 -*- import subprocess child = subprocess.Popen(["ping","-c","5","www.baidu.com"]) #child = subprocess.Popen("ping -c5 www.baidu.com",shell=True) print("parent process") print child
父进程在开启子进程之后没有等到其完成,而是直接print
改成等待模式:
[root@typhoeus79 20130925]# ./sub_popen.py PING www.a.shifen.com (220.181.112.143) 56(84) bytes of data. --- www.a.shifen.com ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 4001ms parent process <subprocess.Popen object at 0x7fe424c34050> [root@typhoeus79 20130925]# more sub_popen.py #!/usr/bin/env python26 #-*- coding:utf8 -*- import subprocess child = subprocess.Popen(["ping","-c","5","www.baidu.com"]) child.wait() print("parent process") print child
父进程中对子进程进行其他操作:
child.poll() #检查子进程状态
child.kill() #终止子进程
child.send_signal() #向子进程发送信号
child.terminate() #终止子进程
子进程的PID存储在child.pid中
子进程的文本流控制
子进程的标准输入、标准输出、标准错误通过如下属性:
{'_child_created': True, 'returncode': 1, 'stdout': None, 'stdin': None, 'pid': 7070, 'stderr': None, 'universal_newlines': False}
child.stdin
child.stdout
child.stderr
可以在Popen()建立子进程的时候改变标准输入、标准输出和标准错误,并可以利用subprocess.PIPE将多个子进程的输入和输出在一起,构成管道pipe:
[root@typhoeus79 20130925]# more sub_pipe.py #!/usr/bin/env python26 #-*- coding:utf8 -*- import subprocess child1 = subprocess.Popen(["ls","-l"],stdout=subprocess.PIPE) child2 = subprocess.Popen(["wc"],stdin=child1.stdout,stdout=sub process.PIPE) out = child2.communicate() print out [root@typhoeus79 20130925]# ./sub_pipe.py (' 4 29 167\n', None)
1、child1的stdout将文本输出缓存到subprocess.PIPE中
2、child2的stdin从child1的stdout读取文本
3、child2的输出文本也被存储在subprocess.PIPE中
4、communicate()方法从PIPE中读取相应的文本
communicate是Popen对象的一个方法,该方法会阻塞父进程,直到子进程完成。
communicate(input=None) Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate. The optional input argument should be a string to be sent to the child process, or None, if no data should be sent to the child. communicate() returns a tuple (stdout, stderr). Note: The data read is buffered in memory, so do not use this method if the data size is large or unlimited.
可以使用communicate()方法使用PIPE给子进程输入:
#!/usr/bin/env python26 #-*- coding:utf8 -*- import subprocess import time child = subprocess.Popen(["cat"],stdin=subprocess.PIPE) time.sleep(5) child.communicate("Hello\n")
通过time.sleep也可以看到communicate是阻塞父进程
对python执行系统命令的封装
def sys_command(system_cmd): logger.debug("system_cmd = '%s'." %system_cmd) pipe = subprocess.Popen(system_cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True,stdin=subprocess.PIPE) stdout, stderr = pipe.communicate() returncode = pipe.returncode logger.debug("returncode = '%d'." %returncode) logger.debug("stdout = '%s'." %stdout) logger.debug("stderr = '%s'." %stderr) return returncode,stdout,stderr