Connect to an existing Docker container and start an interactive shell (terminal / tty).

dterm.sh

dterm() {
  # args as `[PROJECT_NAME] [SERVICE_NAME]` or `[CONTAINER_NAME]`
  [ -z "$2" ] && CONTAINER_BASE_NAME="$1" || CONTAINER_BASE_NAME="${1}_${2}"

  CONTAINER_NAME=$(docker ps --format "{{.Names}}" | grep ^${CONTAINER_BASE_NAME})

  if [ $(printf "$CONTAINER_NAME" | wc -l) -gt 1 ]; then
    echo "\e[1;31m[!] Multiple container names match \"$CONTAINER_BASE_NAME.\""
    echo ">>> If project, add specificity as \`dockertty [PROJECT_NAME] [SERVICE_NAME]\`.\e[0m"
    return
  fi

  # find container's installed shells
  BIN_LS=$(docker exec "$CONTAINER_NAME" ls /bin)

  if [ ! -z $(echo "$BIN_LS" | grep "^bash$") ]; then
    TARGET_SHELL="bash"
  else
    if [ ! -z $(echo "$BIN_LS" | grep "^ash$" ) ]; then
      TARGET_SHELL="ash"
    else
      TARGET_SHELL="sh"
    fi
  fi

  docker exec -it "$CONTAINER_NAME" "/bin/${TARGET_SHELL}"
}

I got tired of typing docker exec -it <container_full_name> /bin/ash, so I made this function to truncate keystrokes down to dterm <project> <service>.

Hooray.