Copyright (c) 2009, Sun Microsystems Inc. All Rights Reserved.
The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License. You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.
See the License for the specific language governing permissions and limitations under the License. When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with
the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
#include <stdlib.h> int daemon(int nochdir, int noclose);
The daemon() function provides a means for applications to run in the background.
This function ensures that the process calling this function:
runs in the background
detaches from the controlling terminal
forms a new process group
is not a session group leader.
The arguments to this function are treated as boolean variables and are evaluated using negative logic.
If the nochdir argument is zero the working directory will be changed to the root directory (/); otherwise it will not be.
If the noclose argument is zero the descriptors 0, 1, and 2 (normally corresponding to standard input, output and error output, depending on the application) will be redirected to /dev/null; otherwise they will not be.
Upon successful completion, daemon() returns 0. Otherwise it returns -1 and sets errno to the values specified for fork(2), setsid(2), open(2), and dup(2).
If daemon() is called with noclose set to 0 and fails to redirect descriptors 0, 1, and 2 to /dev/null, those descriptors are not guaranteed to be the same as before the call.
Example 1 Using daemon to run a process in the background.
The main() function of a network server could look like this:
int background; /* background flag */ /* Load and verify the configuration. */ /* Go into background. */ if (background && daemon(0, 0) < 0) err(1, "daemon"); /* Process requests here. */
See attributes(7) for descriptions of the following attributes:
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| Interface Stability Committed |
| MT-Level Async-Signal-Safe |
Intro (2), dup (2), fork (2), open (2), setsid (2), attributes (7)