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,24,11,8,7max=40passphrase=3match=4similar=deny
random=47enforce=everyone
retry=3Out[6]: 0
2 os.popen()
可以返回运行结果
popen(command [, mode='r'[, bufsize]]) ->pipe
Open a pipe to/froma command returning a file object.
运行返回结果
In [20]: output = os.popen('cat /PRoc/cpuinfo')
In [21]: lineLen =[]
In [22]:forlineinoutput.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()andreturnstatus, output.
Interface summary:importcommands
outtext=commands.getoutput(cmd)
(exitstatus, outtext)=commands.getstatusoutput(cmd)
outtext= commands.getstatus(file)#returns output of "ls -ld file"A trailing newlineisremovedfromthe output string.
Encapsulates the basicOperation:
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
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)ifretcode <0:print>>sys.stderr,"Child was terminated by signal", -retcodeelse:print>>sys.stderr,"Child returned", retcodeexceptOSError, 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)
total42244
-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)