Python Popen input from variable?

Question

I am trying to use Popen to run a java program that takes a few arguments, the last of them is a xml template.

What I have so far attempts to pass the value of the template through communicate(), but it doesn't seem to work.

command = [
        'java',
        '-jar',
        '~/jenkins-cli.jar',
        '-noKeyAuth',
        '-s',
        'docker-host',
        'create-job',
        (self.project.project_name+'-'+env)
    ]

subprocess.Popen(command,
                 stdin=subprocess.PIPE,
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE
                 ).communicate(input=template.render(template_vars))

I know for a fact that the value of template.render(template_vars) is correct, I can use the output from that function call on the command line and it works perfectly, the issue is only in passing the value to the process.

If I run the following from the command line everything works.

java -jar ~/jenkins-cli.jar -noKeyAuth -s jenkins-host create-job test-dev < template.xml

Is there a better way to send the output of template.render(template_vars) as input to the process?

"the last of them is an xml template" doesn't seem to be true; it seems like that XML template is the stdin of the Java program, not a command-line argument. — abarnert
– abarnert, Commented Dec 2, 2014 at 22:46

abarnert · Accepted Answer · 2014-12-02 22:45:39Z

2

I don't think your problem is the input here, but rather the arguments. In particular:

'~/jenkins-cli.jar',

On the command line, you get shell tilde expansion for free. But when using subprocess (or calling exec-family functions from any language, as subprocess does), you have to do it manually, like this:

os.path.expanduser('~/jenkins-cli.jar'),

Also, you're passing a different value for the -s option ('docker-host' instead of 'jenkins-host'), and for the project name ('something-env' instead of 'test-dev'), so the fact that the command line works doesn't really show that your code should work.

As a side note, if you're trying to debug your code, ignoring the stdout, stderr, and return code seems pretty silly. Print them out and see what you get, like this:

p = Popen(command, …)
out, err = p.communicate(input=…)
print(p.returncode, out, err)

Or, of course, don't capture the stdout and stderr in the first place, so they just print to the console.

edited Dec 2, 2014 at 22:45

answered Dec 2, 2014 at 22:40

abarnert

368k54 gold badges626 silver badges691 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Colin Murphy Over a year ago

It was ~ that was messing things up for me, thanks I completely missed my use of it.The issue with me saying jenkins-host vs docker-host was a typo on my part, in the actual code it specifies the url for my jenkins master which I was removing, the second time It typed it I just screwed up and typed docker since I've been using it so much. Thanks for the help.

Collectives™ on Stack Overflow

Python Popen input from variable?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related