python之subprocess

Posted 2020-10-03

官网介绍：https://docs.python.org/3/library/subprocess.html

Popen():
[[email protected] scripts]# cat sub_popen.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.Popen([‘ls‘,‘-l‘],shell=True)
print(type(child))
print(‘parent‘)
[[email protected] scripts]# python sub_popen.py 
<class ‘subprocess.Popen‘>
parent
stu_subprocess.py  sub_popen.py

如果将不添加shell，使用默认的：
[[email protected] scripts]# cat sub_popen.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.Popen([‘ls‘,‘-l‘],shell=False)      shell参数默认为False
print(type(child))
print(‘parent‘)
[[email protected] scripts]# python sub_popen.py 
<class ‘subprocess.Popen‘>
parent
total 8
-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py
-rw-r--r-- 1 root root 136 Aug 21 15:41 sub_popen.py

Popen不会阻塞父进程运行，Popen启动新的进程与父进程并行执行，默认父进程不等待新进程结束。

[[email protected] scripts]# cat test_subprocess.py
#!/usr/bin/python
#coding=utf8
 
def TestPopen():
import subprocess
p = subprocess.Popen([‘ls‘,‘-l‘],shell=True)
for i in range(5):
print("other things")
 
print(TestPopen())
[[email protected] scripts]# python test_subprocess.py
other things
other things
other things
other things
other things
None
stu_subprocess.py sub_call.py sub_check_output.py sub_popen.py sub_run.py test_subprocess.py
 
[[email protected] scripts]# cat test_subprocess1.py
#!/usr/bin/python
#coding=utf8
 
wait(): 阻塞父进程，等待子进程运行结束再继续运行父进程
def TestWait():
import subprocess
import datetime
print(datetime.datetime.now())
p = subprocess.Popen(‘sleep 10‘,shell=True)
p.wait() wait()阻塞了父进程的运行，等待子进程运行完成后才继续运行父进程
print(p.returncode)
print(datetime.datetime.now())
 
TestWait()
[[email protected] scripts]# python test_subprocess1.py
2017-08-21 16:49:15.061676
0 当子进程运行完成结束后，返回code为0
2017-08-21 16:49:25.066657
 
poll():判断子进程是否结束
[[email protected] scripts]# cat test_subprocess2.py
#!/usr/bin/python
#coding=utf8
 
def TestWait():
import subprocess
import datetime,time
print(datetime.datetime.now())
p = subprocess.Popen(‘sleep 10‘,shell=True) 子进程要睡眠10秒
t = 1
while (t <= 5):
time.sleep(1)
p.poll() 执行判断子进程，这里花了5秒
print(p.returncode)
t = t + 1
print(datetime.datetime.now())
 
TestWait()
[[email protected] scripts]# python test_subprocess2.py
2017-08-21 16:56:33.672417
None
None
None
None
None
2017-08-21 16:56:38.684795
 
kill()或者terminate()： 杀掉子进程
[[email protected] scripts]# cat test_subprocess3.py
#!/usr/bin/python
#coding=utf8
 
def TestKillAndTerminate():
import subprocess
import datetime,time
print(datetime.datetime.now())
p = subprocess.Popen(‘sleep 10‘,shell=True)
t = 1
while (t <= 5):
time.sleep(1)
t = t + 1
p.kill()
print(datetime.datetime.now())
 
TestKillAndTerminate()
[[email protected] scripts]# python test_subprocess3.py
2017-08-21 17:03:16.315531
2017-08-21 17:03:21.329266
可以看见子进程只运行了5秒

[[email protected] scripts]# cat sub_popen.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.Popen([‘ls‘,‘-l‘],shell=False)
child.wait()               阻塞父进程，直到子进程运行完成
print(type(child))
print(‘parent‘)
[[email protected] scripts]# python sub_popen.py 
total 12
-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py
-rw-r--r-- 1 root root 135 Aug 21 15:47 sub_call.py
-rw-r--r-- 1 root root 149 Aug 21 15:47 sub_popen.py
<class ‘subprocess.Popen‘>
parent
可以看出先运行的子进程，最后才是父进程，等待子进程运行后，再运行父进程
除了wait()之外还有如下：
child.poll() # 检查子进程状态
child.kill() # 终止子进程
child.send_signal() # 向子进程发送信号
child.terminate() # 终止子进程
子进程的PID存储在child.pid
子进程的标准输入、标准输出和标准错误如下属性分别表示:
child.stdin
child.stdout
child.stderr

subprocess.PIPE实际上为文本流提供一个缓存区。child的stdout将文本输出到缓存区，然后打印出缓存区的内容：
[[email protected] scripts]# cat sub_popen.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.Popen([‘ls‘,‘-l‘],shell=False,stdout=subprocess.PIPE)
print(child.stdout.read().decode(‘utf-8‘))      打印缓存区内容，由于是bytes格式，所以转码
print(‘parent‘)
[[email protected] scripts]# python sub_popen.py 
total 16
-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py
-rw-r--r-- 1 root root 148 Aug 21 15:53 sub_call.py
-rw-r--r-- 1 root root 183 Aug 21 16:07 sub_popen.py
-rw-r--r-- 1 root root 147 Aug 21 15:56 sub_run.py

parent

communicate()
Popen.communicate(input=None)：与子进程进行交互。向stdin发送数据，或从stdout和stderr中读取数据。可选参数input指定发送到子进程的参数。Communicate()返回一个元组：(stdoutdata, stderrdata)。注意：如果希望通过进程的stdin向其发送数据，在创建Popen对象的时候，参数stdin必须被设置为PIPE。同样，如果希望从stdout和stderr获取数据，必须将stdout和stderr设置为PIPE。
[[email protected] scripts]# cat sub_popen.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.Popen([‘ls‘,‘-l‘],shell=False,stdout=subprocess.PIPE)
#print(child.stdout.read().decode(‘utf-8‘))
print(child.communicate())          返回的是标准输出，标准错误输出的tuple
print(‘parent‘)
[[email protected] scripts]# python sub_popen.py 
(b‘total 16\n-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py\n-rw-r--r-- 1 root root 148 Aug 21 15:53 sub_call.py\n-rw-r--r-- 1 root root 211 Aug 21 16:11 sub_popen.py\n-rw-r--r-- 1 root root 147 Aug 21 15:56 sub_run.py\n‘, None)    NONE就是标准错误输出结果
parent
可以看见先输出的子进程内容，然后才是父进程，communicate()是Popen对象的一个方法，该方法会阻塞父进程，直到子进程完成
[[email protected] scripts]# cat sub_popen.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child1 = subprocess.Popen([‘cat‘,‘/etc/passwd‘],shell=False,stdout=subprocess.PIPE)
child2 = subprocess.Popen([‘grep‘,‘0:0‘],stdin=child1.stdout, stdout=subprocess.PIPE)
#  subprocess.PIPE实际上为文本流提供一个缓存区。child1的stdout将文本输出到缓存区，随后child2的stdin从该PIPE中将文本读取走。child2的输出文本也被存放在PIPE中，直到communicate()方法从PIPE中读取出PIPE中的文本。
out,err = child2.communicate()   因为communicate()返回的是一个元祖
print(out)     纸打印出标准输出内容
print(‘parent‘)
[[email protected] scripts]# python sub_popen.py 
b‘root:x:0:0:root:/root:/bin/bash\n‘
parent

child1.stdout-->subprocess.PIPE
child2.stdin<--subprocess.PIPE
child2.stdout-->subprocess.PIPE

利用communicate()实现交互：
[[email protected] scripts]# cat stu_subprocess.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child1 = subprocess.Popen([‘python‘],stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
out,err = child1.communicate(b‘print("hello")\nexit()‘)       继续给子进程输入信息
# 启动一个子进程，然后控制其输入和输出
print(out.decode(‘utf-8‘))
print(‘parent‘)
[[email protected] scripts]# python stu_subprocess.py 
hello

parent

[[email protected] scripts]# cat sub_popen2.py 
#!/usr/bin/python
#coding=utf8

import subprocess
 
obj = subprocess.Popen(["python"], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
obj.stdin.write(b‘print("hello")\n‘)         stdin.write和communicate两者交换使用
obj.stdin.write(b‘print("world")‘)
 
out,err = obj.communicate()
print(out)
[[email protected] scripts]# python sub_popen2.py 
b‘hello\nworld\n‘

call():
subprocess.call()
父进程等待子进程完成
返回退出信息(returncode，相当于Linux exit code)
[[email protected] scripts]# cat sub_call.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.call([‘ls‘,‘-l‘],shell=False)
print(type(child))
print(‘parent‘)
[[email protected] scripts]# python sub_call.py 
total 12
-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py
-rw-r--r-- 1 root root 135 Aug 21 15:45 sub_call.py
-rw-r--r-- 1 root root 136 Aug 21 15:41 sub_popen.py
<class ‘int‘>                call函数返回的是int
parent
调用call函数可以明显看出子进程阻塞了主进程的运行，先运行子进程，最后才是主进程
[[email protected] scripts]# cat sub_call.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.call([‘ls‘,‘-l‘],shell=False)
print(type(child))
print(child)                  ----->returncode
print(‘parent‘)
[[email protected] scripts]# python sub_call.py        
total 12
-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py
-rw-r--r-- 1 root root 148 Aug 21 15:53 sub_call.py
-rw-r--r-- 1 root root 149 Aug 21 15:47 sub_popen.py
<class ‘int‘>
0
parent
subprocess.call(*popenargs, **kwargs)：运行命令。该函数将一直等待到子进程运行结束，并返回进程的returncode。如果子进程不需要进行交互,就可以使用该函数来创建。
call函数返回的是returncode，也就是int类型

根据shell类型不同，可以更改传入call函数的args类型：
[[email protected] scripts]# cat sub_call.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.call("ls -l",shell=True)       
print(type(child))
print(child)
print(‘parent‘)
shell=True参数会让subprocess.call接受字符串类型的变量作为命令，并调用shell去执行这个字符串，当shell=False是，subprocess.call只接受数组变量作为命令，并将数组的第一个元素作为命令，剩下的全部作为该命令的参数。
[[email protected] scripts]# python sub_call.py 
total 40
-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py
-rw-r--r-- 1 root root 143 Aug 21 17:22 sub_call.py
-rw-r--r-- 1 root root 143 Aug 21 16:33 sub_check_output.py
-rw-r--r-- 1 root root 162 Aug 21 17:17 sub_getoutput.py
-rw-r--r-- 1 root root 279 Aug 21 16:17 sub_popen.py
-rw-r--r-- 1 root root 148 Aug 21 16:29 sub_run.py
-rw-r--r-- 1 root root 257 Aug 21 16:53 test_subprocess1.py
-rw-r--r-- 1 root root 340 Aug 21 16:52 test_subprocess2.py
-rw-r--r-- 1 root root 332 Aug 21 17:03 test_subprocess3.py
-rw-r--r-- 1 root root 183 Aug 21 16:44 test_subprocess.py
<class ‘int‘>
0
parent
所以当shell默认为False时，args传入的值必须是列表，而不能是str
from subprocess import call  
import shlex  
cmd = "cat test.txt; rm test.txt"  
call(cmd, shell=True)
shell介绍：
https://zhidao.baidu.com/question/651286079254739125.html

3.5新增的run()：
class subprocess.CompletedProcess
The return value from run(), representing a process that has finished.
[[email protected] scripts]# cat sub_run.py 
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.run([‘ls‘,‘-l‘],shell=False)
print(type(child))
print(child)
print(‘parent‘)
[[email protected] scripts]# python sub_run.py 
total 16
-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py
-rw-r--r-- 1 root root 148 Aug 21 15:53 sub_call.py
-rw-r--r-- 1 root root 149 Aug 21 15:47 sub_popen.py
-rw-r--r-- 1 root root 147 Aug 21 15:56 sub_run.py
<class ‘subprocess.CompletedProcess‘>
CompletedProcess(args=[‘ls‘, ‘-l‘], returncode=0)
parent

check_output():
[[email protected] scripts]# cat sub_check_output.py
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.check_output([‘ls‘,‘-l‘],shell=False)
print(type(child))
print(child)
print(‘parent‘)
[[email protected] scripts]# python sub_check_output.py
<class ‘bytes‘>
b‘total 20\n-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py\n-rw-r--r-- 1 root root 148 Aug 21 15:53 sub_call.py\n-rw-r--r-- 1 root root 156 Aug 21 16:26 sub_check_output.py\n-rw-r--r-- 1 root root 279 Aug 21 16:17 sub_popen.py\n-rw-r--r-- 1 root root 147 Aug 21 15:56 sub_run.py\n‘
parent
 
[[email protected] scripts]# cat sub_check_output.py
#!/usr/bin/python
#coding=utf8
import subprocess
child = subprocess.check_output([‘ls‘,‘-l‘],shell=False)
print(type(child))
print(‘parent‘)
[[email protected] scripts]# python sub_check_output.py
<class ‘bytes‘>
parent
并没有打印出子进程运行后的内容

subprocess.getoutput(cmd),返回的是一个字符串
Return output (stdout and stderr) of executing cmd in a shell.
[[email protected] scripts]# python sub_getoutput.py 
<class ‘str‘>
stu_subprocess.py
sub_call.py
sub_check_output.py
sub_getoutput.py
sub_popen.py
sub_run.py
test_subprocess1.py
test_subprocess2.py
test_subprocess3.py
test_subprocess.py
[[email protected] scripts]# cat sub_getoutput.py 
#!/usr/bin/python
#coding=utf8

import subprocess

def TestGetOutput():
  outp = subprocess.getoutput(["ls" ,"-l"])      列表
  print(type(outp))
  print(outp)

TestGetOutput()
[[email protected] scripts]# cat sub_getoutput.py 
#!/usr/bin/python
#coding=utf8

import subprocess

def TestGetOutput():
  outp = subprocess.getoutput("ls -l")        字符串
  print(type(outp))
  print(outp)

TestGetOutput()
[[email protected] scripts]# python sub_getoutput.py 
<class ‘str‘>
total 40
-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py
-rw-r--r-- 1 root root 148 Aug 21 15:53 sub_call.py
-rw-r--r-- 1 root root 143 Aug 21 16:33 sub_check_output.py
-rw-r--r-- 1 root root 162 Aug 21 17:17 sub_getoutput.py
-rw-r--r-- 1 root root 279 Aug 21 16:17 sub_popen.py
-rw-r--r-- 1 root root 148 Aug 21 16:29 sub_run.py
-rw-r--r-- 1 root root 257 Aug 21 16:53 test_subprocess1.py
-rw-r--r-- 1 root root 340 Aug 21 16:52 test_subprocess2.py
-rw-r--r-- 1 root root 332 Aug 21 17:03 test_subprocess3.py
-rw-r--r-- 1 root root 183 Aug 21 16:44 test_subprocess.py

#接收字符串格式命令，返回元组形式，第1个元素是执行状态，第2个是命令结果 
>>> subprocess.getstatusoutput(‘ls -l‘)     
(0, ‘total 40\n-rw-r--r-- 1 root root 256 Aug 21 15:26 stu_subprocess.py\n-rw-r--r-- 1 root root 143 Aug 21 17:22 sub_call.py\n-rw-r--r-- 1 root root 143 Aug 21 16:33 sub_check_output.py\n-rw-r--r-- 1 root root 162 Aug 21 17:17 sub_getoutput.py\n-rw-r--r-- 1 root root 279 Aug 21 16:17 sub_popen.py\n-rw-r--r-- 1 root root 148 Aug 21 16:29 sub_run.py\n-rw-r--r-- 1 root root 257 Aug 21 16:53 test_subprocess1.py\n-rw-r--r-- 1 root root 340 Aug 21 16:52 test_subprocess2.py\n-rw-r--r-- 1 root root 332 Aug 21 17:03 test_subprocess3.py\n-rw-r--r-- 1 root root 183 Aug 21 16:44 test_subprocess.py‘)