Running Jar files from Python

Question

I want to make a program that can execute jar files and print whatever the jar file is doing in my python program but without using the windows command line, I have searched all over the web but nothing is coming up with how to do this.

My program is a Minecraft server wrapper and I want it to run the server.jar file and instead of running it within the windows command prompt I want it to run inside the Python shell.

Any ideas?

Hi Daniel, what is the purpose of wanting to listen in on what other applications are doing? Is it the logs you want to listen to or something else? Network traffic? Something else? Please provide some more detail to paint a healthy picture of your problem. Hope this helps! — jamesmortensen, Jun 23 '13 at 04:24
There is some more info now, Hope that helps explaining what Im doing. — Dan Alexander, Jun 23 '13 at 04:33

score 10 · Accepted Answer · edited Jun 23 '13 at 15:44

10

First you have to execute the program. A handy function for doing so:

def run_command(command):
    p = subprocess.Popen(command,
                     stdout=subprocess.PIPE,
                     stderr=subprocess.STDOUT)
    return iter(p.stdout.readline, b'')

It will return an iterable with all the lines of output.
And you can access the lines and print using

for output_line in run_command('java -jar jarfile.jar'):
    print(output_line)

add also import subprocess, as run_command uses subprocess.

edited Jun 23 '13 at 15:44

Ry-

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answered Jun 23 '13 at 04:30

svineet

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I get an error saying b'Error: Could not find or load main class craftbukkit.jar\r\n', so what do i do. – Dan Alexander Jun 23 '13 at 04:36
the output is originally from the jvm, so i suppose your java code has some bug. – svineet Jun 23 '13 at 04:39
well it is just a minecraft server jar file – Dan Alexander Jun 23 '13 at 04:40
oops, the command should be java -jar jarfile.jar, sorry. Correcting error now. – svineet Jun 23 '13 at 04:43
Ok now it is working but the java console is open so is there a wayto hide this? – Dan Alexander Jun 23 '13 at 04:46
what do you mean by java console? Do you mean that the python program is executing in a command prompt window? – svineet Jun 23 '13 at 04:50
No a command prompt looking window with the java logo on it comes up – Dan Alexander Jun 23 '13 at 04:57
That is all i can do, i don't know of any method to do what you want. Sorry :( My suggestion is if you want to enter command too, run it directly from the command line. – svineet Jun 23 '13 at 04:58
@Daniel Alexander to write something to your subprocess yous should stdin=subprocess.PIPE then `p.stdin.write("my command\n");p.stdin.flush()` – Xavier Combelle Jun 23 '13 at 11:38
I had to add and extra shell=True feature to the subprocess.Popen statement in order to make it work for me. Don't what what the ups and downs of using a shell=True is, though! – Bikash Gyawali Oct 29 '14 at 14:13

Running Jar files from Python

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