Develop Reference

Stopping bash running in a python script

I am writing a python script that calls a bash script.
from subprocess import call
rc = call("./try_me.sh")
How can I exit the running bash file without exiting the running python script?
I need something like Ctrl + C.

There's different ways to approach this problem.
It appears that you're writing some sort of CLI tool since you referenced Ctrl+C. If that's the case you can use & and send a SIGINT signal to stop it when you need.
import os
os.system('nohup ./try_me.sh &')
If you want stricter control try using async subprocess management:
https://docs.python.org/3/library/asyncio-subprocess.html

After Some research, I found I should have used Popen to run the bash file as #AKX suggested.
from subprocess import Popen
r1 = Popen('printf "*Systempassword* \n" |sudo -S ./try_me.sh &', shell=True, preexec_fn=os.setsid))
when you need to stop running the bash file
import os
os.killpg(os.getpgid(r1.pid), signal.SIGTERM) # Send the signal to all the process groups

Start a background shell script from python

I would like to connect a remote machine and run background script in that machine from python.
I tried:
os.system("ssh root#10.0.0.1 \' nohup script.sh & \')
But it seems not working. And if I put nohup in script.sh, and simply run
os.system("ssh root#10.0.0.1 \' script.sh \'")
The nohup command would not work in either cases.
I'm confused why so, and is there anybody knows how to do background job from python or it's just impossible doing it this way?

What kind of errors are you getting? What version of Python are you using?
You should take a look at this Python subprocess - run multiple shell commands over SSH
import subprocess
sshProcess = subprocess.Popen(["ssh", "root#10.0.0.1"],
stdin=subprocess.PIPE,
stdout = subprocess.PIPE,
universal_newlines=True,
bufsize=0)
sshProcess.stdin.write("nohup script.sh &")

For example you have a local script (python, bash, etc. Here I am demonstrating you using a python script)
First you create a python file locally. Lets say hello.py
# 'hello.py'
import os
print os.system('hostname')
Secondly now a python script which would execute the above hello.py on a remote machine
import pathos
copy = pathos.core.copy('hello.py', destination='abc.remote.com:~/hello.py')
exec = pathos.core.execute('python hello.py', host='.remote.com')
print exec.response()

Calling a subprocess in python with environmental variables

I am trying to write a python script to automatically scan a section of plex using the Plex Media Scanner. To do so, I must run the scanner as the user running plex (in this case it is 'plex') as well as provide it with the environment variable 'LD_LIBRARY_PATH'. I've tried using both subprocess.call and subprocess.Popen with no difference. In either case, I am not getting any output.
Here is the code I am using:
#!/usr/bin/python
import os
import subprocess
import shlex
env = os.environ.copy()
env['LD_LIBRARY_PATH'] = '/usr/lib/plexmediaserver'
s = "/bin/su - plex -c '/usr/lib/plexmediaserver/Plex\ Media\ Scanner -s -c 2'"
task = shlex.split(s)
exitCode = subprocess.call(task, env=env, shell=True)
Now I already have a working version that does what I want it to do but I had to resort to using a wrapper bash script to do so. You can see the code below:
#!/bin/sh
export LD_LIBRARY_PATH=/usr/lib/plexmediaserver
/usr/lib/plexmediaserver/Plex\ Media\ Scanner $#
And the relevant line of the script which calls it:
exitCode = subprocess.call("/bin/su - plex -c '/var/lib/deluge/delugeScripts/pms.sh -s -c 2'", shell=True)
Thanks for your help.

As jordanm noted in his comment:
the - in su makes it a login shell which re-initializes the environment.

How to make a call to an executable from Python script?

I need to execute this script from my Python script.
Is it possible? The script generate some outputs with some files being written. How do I access these files? I have tried with subprocess call function but without success.
fx#fx-ubuntu:~/Documents/projects/foo$ bin/bar -c somefile.xml -d text.txt -r aString -f anotherString >output
The application "bar" also references to some libraries, it also create the file "bar.xml" besides the output. How do I get access to these files? Just by using open()?
Thank you,
Edit:
The error from Python runtime is only this line.
$ python foo.py
bin/bar: bin/bar: cannot execute binary file

For executing the external program, do this:
import subprocess
args = ("bin/bar", "-c", "somefile.xml", "-d", "text.txt", "-r", "aString", "-f", "anotherString")
#Or just:
#args = "bin/bar -c somefile.xml -d text.txt -r aString -f anotherString".split()
popen = subprocess.Popen(args, stdout=subprocess.PIPE)
popen.wait()
output = popen.stdout.read()
print output
And yes, assuming your bin/bar program wrote some other assorted files to disk, you can open them as normal with open("path/to/output/file.txt"). Note that you don't need to rely on a subshell to redirect the output to a file on disk named "output" if you don't want to. I'm showing here how to directly read the output into your python program without going to disk in between.

The simplest way is:
import os
cmd = 'bin/bar --option --otheroption'
os.system(cmd) # returns the exit status
You access the files in the usual way, by using open().
If you need to do more complicated subprocess management then the subprocess module is the way to go.

For executing a unix executable file. I did the following in my Mac OSX and it worked for me:
import os
cmd = './darknet classifier predict data/baby.jpg'
so = os.popen(cmd).read()
print so
Here print so outputs the result.

SSH Connection with Python 3.0

How can I make an SSH connection in Python 3.0? I want to save a file on a remote computer where I have password-less SSH set up.

I recommend calling ssh as a subprocess. It's reliable and portable.
import subprocess
proc = subprocess.Popen(['ssh', 'user#host', 'cat > %s' % filename],
stdin=subprocess.PIPE)
proc.communicate(file_contents)
if proc.retcode != 0:
...
You'd have to worry about quoting the destination filename. If you want more flexibility, you could even do this:
import subprocess
import tarfile
import io
tardata = io.BytesIO()
tar = tarfile.open(mode='w:gz', fileobj=tardata)
... put stuff in tar ...
proc = subprocess.Popen(['ssh', 'user#host', 'tar xz'],
stdin=subprocess.PIPE)
proc.communicate(tardata.getvalue())
if proc.retcode != 0:
...

You want all of the ssh-functionality implemented as a python library? Have a look at paramiko, although I think it's not ported to Python 3.0 (yet?).
If you can use an existing ssh installation you can use the subprocess way Dietrich described, or (another way) you could also use pexpect (website here).

First:
Two steps to login via ssh without password
in your terminal
[macm#macm ~]$ ssh-keygen
[macm#macm ~]$ ssh-copy-id -i $HOME/.ssh/id_rsa.pub root#192.168.1.XX <== change
Now with python
from subprocess import PIPE, Popen
cmd = 'uname -a'
stream = Popen(['ssh', 'root#192.168.1.XX', cmd],
stdin=PIPE, stdout=PIPE)
rsp = stream.stdout.read().decode('utf-8')
print(rsp)

It might take a little work because "twisted:conch" does not appear to have a 3.0 variant.

I have written Python bindings for libssh2, that run on Python 2.4, 2.5, 2.6, 2.7 and 3.

libssh2 works great for Python 3.x.
See this Stack Overflow article
How to send a file using scp using python 3.2?