Helper script to have apps in docker run as user and group of project folder.

run_as_user_setup_source.sh

# Add to Docker image and include in other scripts with (using the current directory
# for the user_id and group_id):
# source /path/to/run_as_user_setup_source.sh "$(pwd)"

# Requires commands:
#  sudo

# Tested on BASH

# Run apps or scripts as the user of the used directory with:
# run_as_user command -args

# The project folder which is binded from the host system. Used passed in folder.
RUN_AS_PROJECT_FOLDER="${1}"

# Get user id and group id of project folder.
RUN_AS_USER_ID=$(stat -c '%u' "${RUN_AS_PROJECT_FOLDER}")
RUN_AS_GROUP_ID=$(stat -c '%g' "${RUN_AS_PROJECT_FOLDER}")

# Check if user and group already exist.
RUN_AS_USER_NAME="$(id -u -n ${RUN_AS_USER_ID} 2> /dev/null)"
RUN_AS_GROUP_NAME="$(getent group ${RUN_AS_GROUP_ID} | cut -d: -f1)"

# Setup user name and group name
# By default, create a random string of 13 lowercase letters.
if [[ -z "${RUN_AS_GROUP_NAME}" ]]; then
  # Create group as it doesn't exist
  RUN_AS_GROUP_NAME="$(tr -dc a-z </dev/urandom | head -c 13 ; echo '')"
  groupadd -g ${RUN_AS_GROUP_ID} -o ${RUN_AS_GROUP_NAME}
fi

if [[ -z "${RUN_AS_USER_NAME}" ]]; then
  # Create user as it doesn't exist
  RUN_AS_USER_NAME="$(tr -dc a-z </dev/urandom | head -c 13 ; echo '')"

  # The home directory to use within the directory within the container.
  RUN_AS_USER_HOME="/home/${RUN_AS_USER_NAME}"

  useradd -u ${RUN_AS_USER_ID} -o -d "${RUN_AS_USER_HOME}" -s /bin/bash -M -g ${RUN_AS_GROUP_ID} ${RUN_AS_USER_NAME} && \
   mkdir -p "${RUN_AS_USER_HOME}" && \
   chown "${RUN_AS_USER_ID}":"${RUN_AS_GROUP_ID}" "${RUN_AS_USER_HOME}"
fi

            
# Change to the shell you wish to use
RUN_AS_SHELL=/bin/sh

# Function definition
function run_as_user() {
  # Change the following to add custom environment variables
  OVERRIDE_ENV="${OVERRIDE_ENV:-}"
  # List of comma-separated Environment variables to preserve into the new environment
  PRESERVE_ENV="${PRESERVE_ENV:-}"
  sudo -n -u "#${RUN_AS_USER_ID}" -g "#${RUN_AS_GROUP_ID}" --preserve-env="${PRESERVE_ENV}" -- "${RUN_AS_SHELL}" -c "${OVERRIDE_ENV} ${*}"
}

# Add setting up any custom folders for user below.  E.q.:
#mkdir -p "${USER_HOME}/.cache" 2> /dev/null
#mkdir -p /go/pkg 2> /dev/null
#chown -R "${USER_ID}":"${GROUP_ID}" "${USER_HOME}/.cache" /go/pkg