Python之系统交互（subprocess）

参考: https://www.cnblogs.com/yyds/p/7288916.html

        https://www.jb51.net/article/133941.htm 

　　https://www.aliyun.com/jiaocheng/454213.html

例子： subprocess执行ansible 命令.

#subprocess 调用ansible命令,没有shell=True要写成列表格式，并且第一个元素是一个可执行的文件       　　

　　child=subprocess.Popen(["ansible","all","-i","./hosts","-m","command","-a","ls /mnt/"], stdout=subprocess.PIPE,stderr=subprocess.PIPE)
　　child.stdout.read()

#带了shell=True,可以直接像在shell在执行命令一样书写要执行的命令

  child=subprocess.Popen(["ansible all  -i ./hosts -m command -a 'ls -alh /mnt/'"], stdout=subprocess.PIPE,stderr=subprocess.PIPE,shell=True)

  child=subprocess.Popen("ansible all  -i ./hosts -m command -a 'ls -alh /mnt/'", stdout=subprocess.PIPE,stderr=subprocess.PIPE,shell=True)

1. communicate()方法:发送data到stdin

下面的例子演示了如何在Python代码中运行命令nslookup www.python.org，这和命令行直接运行的效果是一样的：

import subprocess

print('$ nslookup www.python.org')
r = subprocess.call(['nslookup', 'www.python.org'])
print('Exit code:', r)

如果子进程还需要输入，则可以通过communicate()方法输入,：

import subprocess

print('$ nslookup')
p = subprocess.Popen(['nslookup'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
output, err = p.communicate(b'set q=mx
python.org
exit
')
print(output.decode('utf-8'))
print('Exit code:', p.returncode)

上面的代码相当于在命令行执行命令nslookup，然后手动输入：

set q=mx
python.org
exit