CODEWITHSUNDEEP
pythonqemu
Alex
Alex

Reputation: 303

automation of processes by python

I'm trying to write a python script that start a process and do some operations atferward. The commands that I want to automate by script are circled as red in the picture. The problem is that after performing first command, qemu environment will be run and the other commands should be executed on the qemu environment. So I want to know how can I do these commands by an script in python? Because as I know I can do the first command but I do not know how can I do those commands when I am going to qemu environment.

enter image description here

Could you help me how can I do this process?

Upvotes: 4

Views: 3200

Answers (2)

Padraic Cunningham
Padraic Cunningham

Reputation: 180401

First thing that came to mind was pexpect, a quick search on google turned up this blog post automatically-testing-vms-using-pexpect-and-qemu which seems to be pretty much along the lines of what you are doing:

import pexpect

image = "fedora-20.img"
user = "root"
password = "changeme"

# Define the qemu cmd to run
# The important bit is to redirect the serial to stdio
cmd = "qemu-kvm"
cmd += " -m 1024 -serial stdio -net user -net nic"
cmd += " -snapshot -hda %s" % image
cmd += " -watchdog-action poweroff"

# Spawn the qemu process and log to stdout
child = pexpect.spawn(cmd)
child.logfile = sys.stdout

# Now wait for the login
child.expect('(?i)login:')

# And login with the credentials from above
child.sendline(user)
child.expect('(?i)password:')
child.sendline(password)
child.expect('# ')

# Now shutdown the machine and end the process
if child.isalive():
    child.sendline('init 0')
    child.close()

if child.isalive():
    print('Child did not exit gracefully.')
else:
    print('Child exited gracefully.')

You could do it with subprocess.Popen also, checking the stdout for the (qemu) lines and writing to stdin. Something roughly like this:

from subprocess import Popen,PIPE

# pass initial command as list of individual args
p = Popen(["./tracecap/temu","-monitor",.....],stdout=PIPE, stdin=PIPE)
# store all the next arguments to pass
args = iter([arg1,arg2,arg3])
# iterate over stdout so we can check where we are
for line in iter(p.stdout.readline,""):
    # if (qemu) is at the prompt, enter a command
    if line.startswith("(qemu)"):
        arg = next(args,"") 
        # if we have used all args break
        if not arg:
            break
        # else we write the arg with a newline
        p.stdin.write(arg+"\n")
    print(line)# just use to see the output

Where args contains all the next commands.

Upvotes: 1

neves
neves

Reputation: 39173

Don't forget that Python has batteries included. Take a look of the Suprocess module in the standard lib. There a lot of pitfalls managing processes, and the module take care of them all.

You probably want to start a qemu process and send the next commands writing to its standard input (stdin). Subprocess module will allow you to do it. See that qemu has command line options to connect to stdi: -chardev stdio ,id=id

Upvotes: 1

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