README: Explain that there are no incremental backups.
[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 void daemon_init(void)
35 {
36 pid_t pid;
37 int null;
38
39 DSS_INFO_LOG(("daemonizing\n"));
40 pid = fork();
41 if (pid < 0)
42 goto err;
43 if (pid)
44 exit(EXIT_SUCCESS); /* parent exits */
45 /* become session leader */
46 if (setsid() < 0)
47 goto err;
48 if (chdir("/") < 0)
49 goto err;
50 umask(0);
51 null = open("/dev/null", O_RDWR);
52 if (null < 0)
53 goto err;
54 if (dup2(null, STDIN_FILENO) < 0)
55 goto err;
56 if (dup2(null, STDOUT_FILENO) < 0)
57 goto err;
58 if (dup2(null, STDERR_FILENO) < 0)
59 goto err;
60 close(null);
61 return;
62 err:
63 DSS_EMERG_LOG(("fatal: %s\n", strerror(errno)));
64 exit(EXIT_FAILURE);
65 }
66
67 /**
68 * fopen() the given file in append mode.
69 *
70 * \param logfile_name The name of the file to open.
71 *
72 * \return Either calls exit() or returns a valid file handle.
73 */
74 FILE *open_log(const char *logfile_name)
75 {
76 FILE *logfile;
77
78 assert(logfile_name);
79 logfile = fopen(logfile_name, "a");
80 if (!logfile) {
81 DSS_EMERG_LOG(("can not open %s: %s\n", logfile_name,
82 strerror(errno)));
83 exit(EXIT_FAILURE);
84 }
85 setlinebuf(logfile);
86 return logfile;
87 }
88
89 /**
90 * Close the log file of the daemon.
91 *
92 * \param logfile The log file handle.
93 *
94 * It's OK to call this with logfile == \p NULL.
95 */
96 void close_log(FILE* logfile)
97 {
98 if (!logfile)
99 return;
100 DSS_INFO_LOG(("closing logfile\n"));
101 fclose(logfile);
102 }
103
104 /**
105 * Log the startup message.
106 */
107 void log_welcome(int loglevel)
108 {
109 DSS_INFO_LOG(("***** welcome to dss ******\n"));
110 DSS_DEBUG_LOG(("using loglevel %d\n", loglevel));
111 }