1 /*
2 * Copyright (c) 2013 Ralph Irving
3 *
4 * daemonize.c is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * daemonize.c is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with SlimProtoLib; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17 */
18
19 #include "squeezelite.h"
20
21 #include <syslog.h>
22 #include <sys/stat.h>
23
fork_child_handler(int signum)24 void fork_child_handler(int signum)
25 {
26 switch(signum) {
27 case SIGALRM: exit(EXIT_FAILURE); break;
28 case SIGUSR1: exit(EXIT_SUCCESS); break;
29 case SIGCHLD: exit(EXIT_FAILURE); break;
30 }
31 }
32
33 pid_t parent;
init_daemonize()34 void init_daemonize()
35 {
36 pid_t pid, sid;
37
38 /* already a daemon */
39 if ( getppid() == 1 ) return;
40
41 /* Trap signals that we expect to recieve */
42 signal(SIGCHLD,fork_child_handler);
43 signal(SIGUSR1,fork_child_handler);
44 signal(SIGALRM,fork_child_handler);
45
46 /* Fork off the parent process */
47 pid = fork();
48 if (pid < 0) {
49 syslog( LOG_ERR, "unable to fork daemon, code=%d (%s)",
50 errno, strerror(errno) );
51 exit(EXIT_FAILURE);
52 }
53
54 /* If we got a good PID, then we can exit the parent process. */
55 if (pid > 0) {
56
57 /* Wait for confirmation from the child via SIGTERM or SIGCHLD, or
58 for two seconds to elapse (SIGALRM). pause() should not return. */
59 alarm(2);
60 pause();
61
62 exit(EXIT_FAILURE);
63 }
64
65 /* At this point we are executing as the child process */
66 parent = getppid();
67
68 /* Cancel certain signals */
69 signal(SIGCHLD,SIG_DFL); /* A child process dies */
70 signal(SIGTSTP,SIG_IGN); /* Various TTY signals */
71 signal(SIGTTOU,SIG_IGN);
72 signal(SIGTTIN,SIG_IGN);
73 signal(SIGHUP, SIG_IGN); /* Ignore hangup signal */
74 signal(SIGTERM,SIG_DFL); /* Die on SIGTERM */
75
76 /* Change the file mode mask */
77 umask(0);
78
79 /* Create a new SID for the child process */
80 sid = setsid();
81 if (sid < 0) {
82 syslog( LOG_ERR, "unable to create a new session, code %d (%s)",
83 errno, strerror(errno) );
84 exit(EXIT_FAILURE);
85 }
86
87 /* Change the current working directory. This prevents the current
88 directory from being locked; hence not being able to remove it. */
89 if ((chdir("/")) < 0) {
90 syslog( LOG_ERR, "unable to change directory to %s, code %d (%s)",
91 "/", errno, strerror(errno) );
92 exit(EXIT_FAILURE);
93 }
94 }
95
daemon(int nochdir,int noclose)96 int daemon( int nochdir, int noclose ) {
97
98 if ( ! noclose )
99 {
100 /* Redirect standard files to /dev/null */
101 freopen( "/dev/null", "r", stdin);
102 freopen( "/dev/null", "w", stdout);
103 freopen( "/dev/null", "w", stderr);
104 }
105
106 /* Tell the parent process that we are A-okay */
107 kill( parent, SIGUSR1 );
108
109 return 0;
110 }
111