lib/core/params.js
function (value) {
    const IllegalValue = this.$err.IllegalValue;
    if (typeof value !== 'string') {
      return value;
    }
    const result = value.replace(ENVVAR_PATTERN, function () {
      const varname = arguments[1];
      if (process.env[varname] === undefined) {
        throw new IllegalValue(`Environment variable ${varname} was referenced but not set`);
      }
      return process.env[varname];
    });

    return result;
  }
function (value) {
    const IllegalValue = this.$err.IllegalValue;
    if (typeof value !== 'string') {
      return value;
    }
    const result = value.replace(ENVVAR_PATTERN, function () {
      const varname = arguments[1];
      if (process.env[varname] === undefined) {
        throw new IllegalValue(`Environment variable ${varname} was referenced but not set`);
      }
      return process.env[varname];
    });

    return result;
  }
function ( value ) { const IllegalValue = this . $err . IllegalValue ; if ( typeof value !== 'string' ) { return value ; } const result = value . replace ( ENVVAR_PATTERN , function ( ) { const varname = arguments [ 1 ] ; if ( process . env [ varname ] === undefined ) { throw new IllegalValue ( ` ${ varname } ` ) ; } return process . env [ varname ] ; } ) ; return result ; }
Interpolates config values with the values of the environment variables of the process.

@private
@param {any} value - The value specified for a parameter; possibly an environment variable.
Interpolates config values with the values of the environment variables of the process .