Using python3 to implement Linux scripting functions

Python 3 has been updated for some time. Compared with Python2, there are many different changes. Python 3 is also widely used in Linux. Here we mainly practice some Python3 script execution commands using Linux.

First of all, if you only need to execute, or you only need to get the execution status, you can use os.system to call

#!/usr/bin/env python3
print ('hello,world')
import os
val2 =  os.system('cd trb && cd trb')
val3 = os.system('ls')
print('val2 is ',val2)

the above code. If the code in val2 is executed successfully, that is, there are two levels of trb folders, the value of val2 is 0, otherwise it is 256

The two-line call has no inheritance. If you want to execute continuously, add && (Shell syntax) in one statement )

Before printing, the screen will also display the execution result

hello,worldsh: line 0: cd: trb: 没有那个文件或目录
Abcd.py  automesh.sh  Cal_Ori  fold.txt  Linux_py_temp.py  meshedjob.rec  new_geom  onc143314  trb
val2 is  256

os.popen(cmd) method, you can only get the output of the operation, but if you don’t print, there will be nothing on the screen. .

For example

val4 = os.popen('cd trb && cd trb')
val5 = os.popen('ls')print('开始PRINT')print(val4.read())print(val5.read())

is displayed as follows

hello,world
开始PRINT/bin/sh: line 0: cd: trb: 没有那个文件或目录
Abcd.py
automesh.shCal_Ori
fold.txt
Linux_py_temp.py
meshedjob.rec
new_geom
onc143314
trb

The output here is a file-like object, which can also be used to traverse if read or readlines are called.

Ultimate weapon, subprocess

Recommended module after py3.5 subprocess

Online The commands in the tutorial are functions in 2 and were deleted in 3, but they can be called through subprocessThere are the following commands:subprocess.getstatusoutput
（cmd

）

Return to execute cmd in the shell. (status,

output) Returns a tuple of 2 elements

Add win support after 3.4 subprocess.getoutput（cmd ）

Execute cmd and return the result

legacycmd = subprocess.getstatusoutput('ls -l')print('subprocess.getstatusoutput 输出',legacycmd)
legacycmd2 = subprocess.getoutput('ls -l')print('subprocess.getoutput 输出',legacycmd2)

The above is the output of the code

:

subprocess.getstatusoutput 输出 (0, '总用量 48\n-rwxr--r-- 1 para036 bjpara  516 4月  16 2018 Abcd.py\n-rwxr--r-- 1 para036 bjpara 1619 4月  16 16:58                     automesh_onpsn_fortest.sh\n-rwxr--r-- 1 para036 bjpara 1616 4月  15 14:31 automesh.sh\ndrwxr-xr-x 5 para036 bjpara 4096 4月  15 14:31 Cal_Ori\n-rw-r                    --r-- 1 para036 bjpara   32 4月  16 16:56 fold.txt\n-rwxr--r-- 1 para036 bjpara 1530 4月  15 14:45 Linux_py_temp.py\n-rw-r--r-- 1 para036 bjpara   27                     4月  15 14:43 meshedjob.rec\ndrwxr-xr-x 2 para036 bjpara 4096 4月  15 14:31 new_geom\ndrwxr-xr-x 5 para036 bjpara 4096 4月  15 14:51 onc143314\ndrwx                    r-xr-x 5 para036 bjpara 4096 4月  16 17:05 onc16165650\ndrwxr-xr-x 5 para036 bjpara 4096 4月  16 16:46 onc163840\ndrwxr-xr-x 2 para036 bjpara 4096 4                    月  15 14:32 trb')
subprocess.getoutput 输出 总用量 48
-rwxr--r-- 1 para036 bjpara  516 4月  16 2018 Abcd.py
-rwxr--r-- 1 para036 bjpara 1619 4月  16 16:58 automesh_onpsn_fortest.sh
-rwxr--r-- 1 para036 bjpara 1616 4月  15 14:31 automesh.sh
drwxr-xr-x 5 para036 bjpara 4096 4月  15 14:31 Cal_Ori
-rw-r--r-- 1 para036 bjpara   32 4月  16 16:56 fold.txt
-rwxr--r-- 1 para036 bjpara 1530 4月  15 14:45 Linux_py_temp.py
-rw-r--r-- 1 para036 bjpara   27 4月  15 14:43 meshedjob.rec
drwxr-xr-x 2 para036 bjpara 4096 4月  15 14:31 new_geom
drwxr-xr-x 5 para036 bjpara 4096 4月  15 14:51 onc143314
drwxr-xr-x 5 para036 bjpara 4096 4月  16 17:05 onc16165650
drwxr-xr-x 5 para036 bjpara 4096 4月  16 16:46 onc163840
drwxr-xr-x 2 para036 bjpara 4096 4月  15 14:32 trb

Where output is a string. If you don’t print, it won’t be displayed.

In new versions, it is recommended to use subprocess.run() to solve general problems.

subprocess.run(), subprocess.call(), subprocess.check_call() and subprocess.check_output() are all high-level functions implemented by encapsulating subprocess.Popen, so if we need more complex function, it can be completed through subprocess.Popen

run will not return output by default, only the command and execution status

recomd = subprocess.run(['ls','-l'])#等待命令执行完成后会在屏幕输出执行结果，然后返回一个包含执行结果的CompletedProcess类的实例。print('输出recmd\n',recomd)print(recomd.returncode)

The output is as follows:

If you want to return output, add parameters, pass subprocess.PIPE to stdout and stderr, and then you can pass the stdout and stderr attributes of the returned CompletedProcess class instance or capture the corresponding content;

universal_newlines:

This parameter affects the input and output data format. For example, its value defaults to False. At this time, the output of stdout and stderr is a byte sequence; when the value of this parameter is set to When True, the output of stdout and stderr is a string. The total code is as follows:

#!/usr/bin/env python3
print ('hello,world')
import os
# val2 =  os.system('cd trb && cd trb')
# val3 = os.system('ls')
# print('val2 is ',val2)
# val4 = os.popen('cd trb && cd trb')
# val5 = os.popen('ls')
# print('开始PRINT')
# print(val4.read())
# print(val5.read())
import subprocess
recomd = subprocess.run(['ls','-l'])
#等待命令执行完成后会在屏幕输出执行结果，然后返回一个包含执行结果的CompletedProcess类的实例。
print('输出recmd\n',recomd)
print(recomd.returncode)
print('传递参数')
recomdouterr = subprocess.run( ['ls','-l'],stdout=subprocess.PIPE,stderr=subprocess.PIPE,universal_newlines=True)
print('输出outerr',recomdouterr.stdout,recomdouterr.stderr)
print('传递参数2')
recomdouterr = subprocess.run( ['ls','-l'],stdout=subprocess.PIPE,universal_newlines=True)
print('输出outerr',recomdouterr.stdout)
print(len( recomdouterr.stdout.strip().split('\n') ))
print(recomdouterr.stdout.strip().split('\n')[-1])
# legacycmd = subprocess.getstatusoutput('ls -l')
#
# print('subprocess.getstatusoutput 输出',legacycmd)
#
# legacycmd2 = subprocess.getoutput('ls -l')
#
# print('subprocess.getoutput 输出',legacycmd2)

Reference: python3.5 Official document:

https://docs.python.org/3.5/library/subprocess.html### # #####Python is used more and more widely, and Linux also has great potential as a server. Using Python to implement Linux script operations simplifies server-side operations and improves controllability. ###

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