run: Wait for children to die.
[dss.git] / daemon.c
1 /*
2 * Copyright (C) 1997-2010 Andre Noll <maan@tuebingen.mpg.de>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file daemon.c Some helpers for programs that detach from the console. */
8
9 #include <string.h>
10 #include <stdlib.h>
11 #include <pwd.h>
12 #include <errno.h>
13 #include <sys/types.h>
14 #include <sys/stat.h>
15 #include <grp.h>
16 #include <assert.h>
17 #include <unistd.h>
18 #include <fcntl.h>
19 #include <stdio.h>
20
21 #include "gcc-compat.h"
22 #include "err.h"
23 #include "log.h"
24 #include "str.h"
25 #include "daemon.h"
26
27 /**
28 * Do the usual stuff to become a daemon.
29 *
30 * Fork, become session leader, dup fd 0, 1, 2 to /dev/null.
31 *
32 * \sa fork(2), setsid(2), dup(2).
33 */
34 int daemon_init(void)
35 {
36 pid_t pid;
37 int null, fd[2];
38
39 DSS_INFO_LOG(("daemonizing\n"));
40 if (pipe(fd) < 0)
41 goto err;
42 pid = fork();
43 if (pid < 0)
44 goto err;
45 if (pid) {
46 /*
47 * The parent process exits once it has received one byte from
48 * the reading end of the pipe. If the child exits before it
49 * was able to complete its setup (acquire the lock on the
50 * semaphore), the read() below will return zero. In this case
51 * we let the parent die unsuccessfully.
52 */
53 char c;
54 int ret;
55 close(fd[1]);
56 ret = read(fd[0], &c, 1);
57 if (ret <= 0) {
58 DSS_EMERG_LOG(("child terminated unexpectedly\n"));
59 exit(EXIT_FAILURE);
60 }
61 exit(EXIT_SUCCESS);
62 }
63 close(fd[0]);
64 /* become session leader */
65 if (setsid() < 0)
66 goto err;
67 umask(0);
68 null = open("/dev/null", O_RDWR);
69 if (null < 0)
70 goto err;
71 if (dup2(null, STDIN_FILENO) < 0)
72 goto err;
73 if (dup2(null, STDOUT_FILENO) < 0)
74 goto err;
75 if (dup2(null, STDERR_FILENO) < 0)
76 goto err;
77 close(null);
78 return fd[1];
79 err:
80 DSS_EMERG_LOG(("fatal: %s\n", strerror(errno)));
81 exit(EXIT_FAILURE);
82 }
83
84 /**
85 * fopen() the given file in append mode.
86 *
87 * \param logfile_name The name of the file to open.
88 *
89 * \return Either calls exit() or returns a valid file handle.
90 */
91 FILE *open_log(const char *logfile_name)
92 {
93 FILE *logfile;
94
95 assert(logfile_name);
96 logfile = fopen(logfile_name, "a");
97 if (!logfile) {
98 DSS_EMERG_LOG(("can not open %s: %s\n", logfile_name,
99 strerror(errno)));
100 exit(EXIT_FAILURE);
101 }
102 setlinebuf(logfile);
103 return logfile;
104 }
105
106 /**
107 * Close the log file of the daemon.
108 *
109 * \param logfile The log file handle.
110 *
111 * It's OK to call this with logfile == \p NULL.
112 */
113 void close_log(FILE* logfile)
114 {
115 if (!logfile)
116 return;
117 DSS_INFO_LOG(("closing logfile\n"));
118 fclose(logfile);
119 }
120
121 /**
122 * Log the startup message.
123 */
124 void log_welcome(int loglevel)
125 {
126 DSS_INFO_LOG(("***** welcome to dss ******\n"));
127 DSS_DEBUG_LOG(("using loglevel %d\n", loglevel));
128 }