Redirecting command output in docker
Just a complement, when using docker-compose, you could also try:
command: bash -c "script_or_command > /path/to/log/command.log 2>&1"
When you specify a JSON list as CMD
in a Dockerfile
, it will not be executed in a shell, so the usual shell functions, like stdout and stderr redirection, won't work.
From the documentation:
The exec form is parsed as a JSON array, which means that you must use double-quotes (
"
) around words not single-quotes ('
).Unlike the shell form, the exec form does not invoke a command shell. This means that normal shell processing does not happen. For example,
CMD [ "echo", "$HOME" ]
will not do variable substitution on$HOME
. If you want shell processing then either use the shell form or execute a shell directly, for example:CMD [ "sh", "-c", "echo", "$HOME" ]
.
What your command actually does is executing your index.py
script and passing the strings "1>server.log"
and "2>server.log"
as command-line arguments into that python script.
Use one of the following instead (both should work):
CMD "python index.py > server.log 2>&1"
CMD ["/bin/sh", "-c", "python index.py > server.log 2>&1"]
To use docker run
in a shell pipeline or under shell redirection, making run
accept stdin and output to stdout and stderr appropriately, use this incantation:
docker run -i --log-driver=none -a stdin -a stdout -a stderr ...
e.g. to run the alpine
image and execute the UNIX command cat
in the contained environment:
echo "This was piped into docker" |
docker run -i --log-driver=none -a stdin -a stdout -a stderr \
alpine cat - |
xargs echo This is coming out of docker:
emits:
This is coming out of docker: This was piped into docker