Run a main process in docker container

docker-cmd.sh

#!/usr/bin/env bash
# Break script on any non-zero status of any command
set -e

export DOCKER_CMD_SLEEP

TASK_PID=0

term_handler() {
    if ps -p $TASK_PID > /dev/null; then
        kill -SIGTERM "$TASK_PID"
        # Wait returns status of the killed process and with set -e this breaks the script
        wait "$TASK_PID" || true
    fi

    # SIGTERM comes from docker stop so treat it as normal signal
    exit 0
}

trap 'term_handler' SIGTERM

echo DOCKER_CMD_SLEEP: $DOCKER_CMD_SLEEP

# Periodically executed task
while /bin/true; do
    # Start a main process
    python main.py &
    TASK_PID=$!

    # Sleep in foreground will block traps
    sleep $DOCKER_CMD_SLEEP &
    # All currently active child processes (both task and sleep) are waited for, and the return
    # status is always zero. Thus if the task running longer than sleep amount the wait released
    # only when the task is finished.
    wait
done