1 os.system
可以返回运行shell命令状态，同时会在终端输出运行结果
例如 ipython中运行如下命令，返回运行状态status
os.system(\'cat /etc/passwdqc.conf\') min=disabled,24,11,8,7 max=40 passphrase=3 match=4 similar=deny random=47 enforce=everyone retry=3 Out[6]: 0
2 os.popen()
可以返回运行结果
popen(command [, mode=\'r\' [, bufsize]]) -> pipe Open a pipe to/from a command returning a file object.
运行返回结果
In [20]: output = os.popen(\'cat /proc/cpuinfo\') In [21]: lineLen = [] In [22]: for line in output.readlines(): lineLen.append(len(line)) ....: In [23]: line line lineLen In [23]: lineLen Out[23]: [14, 25, ...
3 如何同时返回结果和运行状态，commands模块:
#String form: <module \'commands\' from \'/usr/lib64/python2.7/commands.pyc\'> File: /usr/lib64/python2.7/commands.py Docstring: Execute shell commands via os.popen() and return status, output. Interface summary: import commands outtext = commands.getoutput(cmd) (exitstatus, outtext) = commands.getstatusoutput(cmd) outtext = commands.getstatus(file) # returns output of "ls -ld file" A trailing newline is removed from the output string. Encapsulates the basic operation: pipe = os.popen(\'{ \' + cmd + \'; } 2>&1\', \'r\') text = pipe.read() sts = pipe.close()
commands示例如下:
In [24]: (status, output) = commands.getstatusoutput(\'cat /proc/cpuinfo\') In [25]: status Out[25]: 0 In [26]: len(output) Out[26]: 3859
4 使用模块subprocess
通常项目中经常使用方法为subporcess.Popen, 我们可以在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连接在一起，构成管道(pipe):
import subprocess child1 = subprocess.Popen(["ls","-l"], stdout=subprocess.PIPE) child2 = subprocess.Popen(["wc"], stdin=child1.stdout,stdout=subprocess.PIPE) out = child2.communicate() print(out)
在例如使用lsblk查看swap分区的uuid：
import subprocess child = subprocess.Popen(["lsblk", "-f"], stdout=subprocess.PIPE) out = child.stdout.readlines() swap_uuid = None for item in out: line = item.strip().split() if len(line) == 4: if(line[1] == \'swap\'): swap_uuid = line[2] print(swap_uuid)
ipython 中运行"?subprocess"可以发现subprocess是python用来替换os.popen()等管道操作命令的新模块
A more real-world example would look like this: try: retcode = call("mycmd" + " myarg", shell=True) if retcode < 0: print >>sys.stderr, "Child was terminated by signal", -retcode else: print >>sys.stderr, "Child returned", retcode except OSError, e: print >>sys.stderr, "Execution failed:", e
相对于上面几种方式，subprocess便于控制和监控进程运行结果,subprocess提供多种函数便于应对父进程对子进程不同要求:
4.1.1 subprocess.call()
父进程父进程等待子进程完成，返回exit code
4.1.2 subprocess.check_call()
父进程等待子进程完成,返回0，如果returncode不为0，则举出错误subprocess.CalledProcessError，该对象包含有returncode属性，可用try...except...来检查
4.1.3 subprocess.check_output()
父进程等待子进程完成
返回子进程向标准输出的输出结果
检查退出信息，如果returncode不为0，则举出错误subprocess.CalledProcessError，该对象包含有returncode属性和output属性，output属性为标准输出的输出结果，可用try...except...来检查
例如:
In [32]: out = subprocess.call("ls -l", shell=True) total 42244 -rw-rw-r--. 1 *** *** 366 May 26 09:10 ChangeLog
4.2.1
上面三个函数都是源于Popen()函数的wapper(封装),如果需要更加个性化应用，那么就需要使用popen()函数
Popen对象创建后，主程序不会自动等待子进程完成。我们必须调用对象的wait()方法，父进程才会等待 (也就是阻塞block)
[wenwt@localhost syntax]$ rm subprocess.pyc [wenwt@localhost syntax]$ python process.py parent process [wenwt@localhost syntax]$ PING www.google.com (173.194.219.99) 56(84) bytes of data. ^C [wenwt@localhost syntax]$ --- www.google.com ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 3999ms
加上wait方法:
[wenwt@localhost syntax]$ python process.py PING www.google.com (173.194.219.103) 56(84) bytes of data. --- www.google.com ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 3999ms parent process
参考文章:Python标准库06 子进程 (subprocess包)