编写Python脚本时, 经常要执行Linux操作系统命令, 如mkdir zzzz. 目前比较推荐的方法是使用subprocess模块.
通过该模块的帮助文档, 可看到其主要提供了4个API, 和相应的使用说明.
Main API
========
call(...): Runs a command, waits for it to complete, then returns
the return code.
check_call(...): Same as call() but raises CalledProcessError()
if return code is not 0
check_output(...): Same as check_call() but returns the contents of
stdout instead of a return code
Popen(...): A class for flexibly executing a command in a new process
结合API的说明来看, 若执行简单的命令, 像前面所说mkdir zzzz, 前三个API都可以, 只是处理细节稍有不同.
In [54]: subprocess.call("mkdir /tmp/zzzz", shell=True)
Out[54]: 0
In [55]: subprocess.call("mkdir /tmp/zzzz", shell=True)
mkdir: cannot create directory `/tmp/zzzz': File exists
Out[55]: 1
In [56]: subprocess.check_call("mkdir /tmp/zzzz", shell=True)
Out[56]: 0
In [57]: subprocess.check_call("mkdir /tmp/zzzz", shell=True)
mkdir: cannot create directory `/tmp/zzzz': File exists
---------------------------------------------------------------------------
CalledProcessError Traceback (most recent call last)
<ipython-input-57-2a531671f16e> in <module>()
----> 1 subprocess.check_call("mkdir /tmp/zzzz", shell=True)
/usr/local/python27/lib/python2.7/subprocess.pyc in check_call(*popenargs, **kwargs)
184 if cmd is None:
185 cmd = popenargs[0]
--> 186 raise CalledProcessError(retcode, cmd)
187 return 0
188
CalledProcessError: Command 'mkdir /tmp/zzzz' returned non-zero exit status 1
In [59]: subprocess.check_output("mkdir /tmp/zzzz", shell=True)
Out[59]: ''
In [60]: subprocess.check_output("mkdir /tmp/zzzz", shell=True)
mkdir: cannot create directory `/tmp/zzzz': File exists
---------------------------------------------------------------------------
CalledProcessError Traceback (most recent call last)
<ipython-input-60-4911eea4ecd3> in <module>()
----> 1 subprocess.check_output("mkdir /tmp/zzzz", shell=True)
/usr/local/python27/lib/python2.7/subprocess.pyc in check_output(*popenargs, **kwargs)
217 if cmd is None:
218 cmd = popenargs[0]
--> 219 raise CalledProcessError(retcode, cmd, output=output)
220 return output
221
CalledProcessError: Command 'mkdir /tmp/zzzz' returned non-zero exit status 1
又若执行复杂的命令或脚本, 需要获取其标准输出, 和标准错误输出, 就要用到Popen接口了. 前三个API, 其实是第四个的简化版, 是将参数直接传给了Popen的构造函数, 不过大部分参数都是保留了默认值, 来看下该构造函数的样子.
def __init__(self, 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):
注意参数shell=False, 其含义为, 是否将args(要执行的命令)置于操作系统的shell环境中运行.
下面给出一个代码段, 用到了Popen, 算是对subprocess模块的小结.
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import subprocess
def exec_cmd(cmd):
proc = subprocess.Popen(cmd, stdout=subprocess.PIPE,
stderr=subprocess.PIPE, shell=True)
stdout, stderr = proc.communicate()
if proc.returncode != 0:
return proc.returncode, stderr
return proc.returncode, stdout
def main():
cmd = "ls -l"
# cmd = "ls -lz"
returncode, stdoutdata = exec_cmd(cmd)
print str(returncode) + " - " + stdoutdata
if __name__ == '__main__':
main()
随时随地看视频
