POSIX shell function to replace __FILE environment variables for Docker

replaceEnvSecrets_1_0_0.inc.sh

# shellcheck disable=SC2120,SC3043
replaceEnvSecrets() {
  # replaceEnvSecrets 1.0.0
  local prefix="${1:-}"

  for envSecretName in $(export | awk '{print $2}' | grep -oE '^[^=]+' | grep '__FILE$'); do
    if [ -z "$prefix" ] || printf '%s' "$envSecretName" | grep "^$prefix" >/dev/null; then
      local envName
      envName=$(printf '%s' "$envSecretName" | sed 's/__FILE$//')

      local filePath
      filePath=$(eval echo '${'"$envSecretName"':-}')

      if [ -n "$filePath" ]; then
        if [ -f "$filePath" ]; then
          echo Using content from "$filePath" file for "$envName" environment variable value.

          export "$envName"="$(cat -A "$filePath")"
          unset "$envSecretName"
        else
          echo ERROR: Environment variable "$envSecretName" is defined but does not point to a regular file. 1>&2
          exit 1
        fi
      fi
    fi
  done
}