docker-entrypoint.sh for ReactApps with pm2 and environment variable substitution on startup

docker-entrypoint.sh

#!/usr/bin/env sh

env | grep "REACT_APP_" | while IFS= read -r line; do
  var=${line%%=*}
  val=$(printf '%s\n' "${line#*=}" | sed -e 's/[\/&]/\\&/g')
  find . -type f -regex '.*\.\(html\|js\|js\.map\|css\|css\.map\|json\|svg\)' \
      -exec sed -i "s/{{$var}}/$val/g" {} +
done

command -v pm2 > /dev/null && status="$?" || status="$?"
if [ "${status}" = 127 ]; then
  yarn global add pm2
fi

PM2_OPTIONS="serve . --no-daemon --spa"

if [ -n "${REACT_APP_BASICAUTH_USERNAME}" ]; then
  PM2_OPTIONS="${PM2_OPTIONS} --basic-auth-username ${REACT_APP_BASICAUTH_USERNAME}"
fi
if [ -n "${REACT_APP_BASICAUTH_PASSWORD}" ]; then
  PM2_OPTIONS="${PM2_OPTIONS} --basic-auth-password ${REACT_APP_BASICAUTH_PASSWORD}"
fi

# shellcheck disable=SC2086
pm2 ${PM2_OPTIONS}