I am currently trying to execute a simple bash command onto my kubernetes pod but seem to be getting some errors which does not make sense.
If I exec into the docker container an run the command plain
I have no name!@kafka-0:/tmp$ if [ $(comm -13 <(sort selectedTopics) <(sort topics.sh) | wc -l) -gt 0 ]; then echo "hello"; fiI get Hello as output.
But if execute the same from the outside as
kubectl exec --namespace default kafka-0 -c kafka -- bash -c "if [ $(comm -13 </tmp/selectedTopics </tmp/topics.sh| wc -l) -gt 0 ]; then echo topic does not exist && exit 1; fi"Then I get an error message stating that /tmp/topics.sh: No such file or directory
event though I able to do this
kubectl exec --namespace $namespace kafka-0 -c kafka -- bash -c "cat /tmp/topics.sh"why does kubectl exec causing me problems?
When you write:
kubectl ... "$(cmd)"cmd is executed on the local host to create the string that is used as the argument to kubectl. In other words, you are executing comm -13 </tmp/selectedTopics </tmp/topics.sh| wc -l on the local host, and not in the pod.
You should use single quotes if you want to avoid expanding locally:
kubectl exec --namespace default kafka-0 -c kafka -- bash -c 'if comm -13 </tmp/topics.sh grep -q . ; then echo topic does not exist >&2 && exit 1; fi'