# 導語
> 在編寫python腳本的時候，偶爾想調用shell命令來執行一些操作會比較方便些。python中目前有多種方法可以達到這樣的目的，有的僅僅是執行命令不返回需要的結果，有些可以返回執行的結果保存到變量，以便于后續操作
> 涉及到的模塊有 `os.system`、`commands`、` subprocess`
---
下面以具體的例子說明情況
```
#!/usr/bin/env bash
import os
import commands
import subprocess
# -- os.system() --
# execute shell command in sub-terminal and can not get the return result
result1 = os.system('ls -l .')
print('result: ')
print(result1)
print('----------------------------------------')
# -- os.popen() --
# execute and can get the return result
result2 = os.popen('ls -l')
# file type
print('type: ', type(result2))
result3 = os.popen('ls -l').readlines()
# list file
print('type: ', type(result3))
print('result: ')
print(result3)
print('----------------------------------------')
# -- commands --
# import commands
# method:
# getoutput
# getstatusoutput
result4 = commands.getoutput('ls -l')
print('result: ')
print(result4)
print('=======')
result5_status, result5_output = commands.getstatusoutput('ls -l')
print('status: ', result5_status)
print('output: ')
print(result5_output)
print('----------------------------------------')
# subprocess
# import subprocess
# method:
# call(["cmd","arg1", "arg2"], shell=True) refer to os.system()
# Popen("cmd", shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT) refer to os.popen
#
#result6 = subprocess.call("ls -l", shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
p = subprocess.Popen('ls *.txt', shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
print(p.stdout.readlines())
for line in p.stdout.readlines():
print line,
## wait for child process to terminate, and turn returncode
retval = p.wait()
## if ok, return 0
print(retval)
```
