how to get STDOUT when the container exit with non-zero code?

[jih-dk]

I run a command in a container with containers.run() method, when an error happened, the container returns a non-zero code, then I can only see the contents og STDERR in ContainerError.

If I correctly understood the codes, when a container exit with non-zero code, it firstly clean the out variable, and collect all STDERR and pass it to ContainerError object.

I would like to see the STDOUT messages before the error happened, is there a way to do that?

[feliperuhland]

Hi @jinxudb

If you use detach=True, you can get the stdout from the container.logs().
Otherwise, you can get from ContainerError.container.logs().
So, you have to catch the exception to get that.

>>> import docker
>>> cli = docker.from_env()
>>> cli.containers.run("python:latest", "python -c 'print(123); exit(1)'")
---------------------------------------------------------------------------
ContainerError                            Traceback (most recent call last)
<ipython-input-5-a3a922806153> in <module>
----> 1 cli.containers.run("python:latest", "python -c 'print(123); exit(1)'")

~/docker-py/docker/models/containers.py in run(self, image, command, stdout, stderr, remove, **kwargs)
    838             container.remove()
    839         if exit_status != 0:
--> 840             raise ContainerError(
    841                 container, exit_status, command, image, out
    842             )

ContainerError: Command 'python -c 'print(123); exit(1)'' in image 'python:latest' returned non-zero exit status 1: b''

>>> a = cli.containers.run("python:latest", "python -c 'print(123); exit(1)'", detach=True)
>>> a.logs()
b'123\n'

>>> try:
...     cli.containers.run("python:latest", "python -c 'print(123); exit(1)'")
... except ContainerError as exc:
...     print(exc.container.logs())
b'123\n'

I hope that helps.
Have a nice day :)