Launch a shell in a Docker container/image

docker-shell.sh

#!/bin/sh
# Author: Jay Dansand
# URL: https://gist.github.com/jaydansand/29744bd44d6ea68611e430a401cb7d14
# Date: May 29 2019, modified June 28 2022

CONTAINER="$1"
if [ -z "$CONTAINER" ]; then
  echo "Usage: `basename $0` container|service [shell command]"
  echo "  Executes shell command (default bash || sh) in a container. If CONTAINER"
  echo "  is not a running Docker container (appearing in 'docker ls -a') then it"
  echo "  will be tested as a docker-compose service or run as an image name."
  exit 1
fi

SHELLCMD="$2"
if [ -z "$SHELLCMD" ]; then
  SHELLCMD='sh -c "if [ `which bash` ]; then bash; else sh; fi"';
fi

# Is it a running container (i.e. use "exec") or an image?
RESULTS=`docker container ls -a 2>/dev/null | cut -f1 -s -d ' ' | tail -n +2 | grep -ci "^$CONTAINER" 2>/dev/null`
RUNNING="$?"

if [ "$RUNNING" -eq 0 ]; then
  # It's running, use exec.
  if [ "$RESULTS" != "1" ]; then
    echo "Given container string matches more than one running container (results: $RESULTS)"
    exit 2
  fi
  echo "Executing shell in $CONTAINER..."
  docker exec -it "$CONTAINER" sh -c "$SHELLCMD"
else
  # Is it docker-compose-based?
  # In theory w/label com.docker.compose.service=$CONTAINER.
  # docker-compose ps --services | grep -P "^${CONTAINER}\$"
  SERVICE=`docker-compose ps --services 2>/dev/null | grep -P "^${CONTAINER}\$" 2>/dev/null`
  IS_SERVICE="$?"
  if [ "$IS_SERVICE" -eq 0 ]; then
    echo "Executing shell in service \"$SERVICE\" via docker-compose..."
    docker-compose exec "$SERVICE" sh -c "$SHELLCMD"
  else
    # It's not running, start an image.
    echo "Running shell in image $CONTAINER..."
    # Use --entrypoint to override any defined automatic command baked into the
    # image. It's a bit roundabit, but we use "sh -c" to launch our command.
    docker run -it --rm --entrypoint="sh" "$CONTAINER" -c "$SHELLCMD"
  fi
fi