gecko-dev/xpcom/threads/nsIEnvironment.idl

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

/**
 * Scriptable access to the current process environment.
 *
 */
[scriptable, uuid(101d5941-d820-4e85-a266-9a3469940807)]
interface nsIEnvironment : nsISupports
{
    /**
     * Set the value of an environment variable.
     *
     * @param aName   the variable name to set.
     * @param aValue  the value to set.
     */
    void set(in AString aName, in AString aValue);

    /**
     * Get the value of an environment variable.
     *
     * @param aName   the variable name to retrieve.
     * @return        returns the value of the env variable. An empty string
     *                will be returned when the env variable does not exist or
     *                when the value itself is an empty string - please use
     *                |exists()| to probe whether the env variable exists
     *                or not.
     */
    AString get(in AString aName);

    /**
     * Check the existence of an environment variable.
     * This method checks whether an environment variable is present in
     * the environment or not.
     *
     * - For Unix/Linux platforms we follow the Unix definition:
     * An environment variable exists when |getenv()| returns a non-NULL value.
     * An environment variable does not exist when |getenv()| returns NULL.
     * - For non-Unix/Linux platforms we have to fall back to a 
     * "portable" definition (which is incorrect for Unix/Linux!!!!)
     * which simply checks whether the string returned by |Get()| is empty
     * or not.
     *
     * @param aName   the variable name to probe.
     * @return        if the variable has been set, the value returned is
     *                PR_TRUE. If the variable was not defined in the
     *                environment PR_FALSE will be returned.
     */
    boolean exists(in AString aName);
};