daemon.c

   1 /*
   2  * Copyright (C) 1997-2008 Andre Noll <maan@systemlinux.org>
   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 "error.h"
  23 #include "log.h"
  24 #include "string.h"
  25
  26 /**
  27  * Do the usual stuff to become a daemon.
  28  *
  29  * Fork, become session leader, dup fd 0, 1, 2 to /dev/null.
  30  *
  31  * \sa fork(2), setsid(2), dup(2).
  32  */
  33 void daemon_init(void)
  34 {
  35         pid_t pid;
  36         int null;
  37
  38         DSS_INFO_LOG("daemonizing\n");
  39         pid = fork();
  40         if (pid < 0)
  41                 goto err;
  42         if (pid)
  43                 exit(EXIT_SUCCESS); /* parent exits */
  44         /* become session leader */
  45         if (setsid() < 0)
  46                 goto err;
  47         if (chdir("/") < 0)
  48                 goto err;
  49         umask(0);
  50         null = open("/dev/null", O_RDONLY);
  51         if (null < 0)
  52                 goto err;
  53         if (dup2(null, STDIN_FILENO) < 0)
  54                 goto err;
  55         if (dup2(null, STDOUT_FILENO) < 0)
  56                 goto err;
  57         if (dup2(null, STDERR_FILENO) < 0)
  58                 goto err;
  59         close(null);
  60         return;
  61 err:
  62         DSS_EMERG_LOG("fatal: %s\n", strerror(errno));
  63         exit(EXIT_FAILURE);
  64 }
  65
  66 /**
  67  * fopen() the given file in append mode.
  68  *
  69  * \param logfile_name The name of the file to open.
  70  *
  71  * \return Either calls exit() or returns a valid file handle.
  72  */
  73 FILE *open_log(const char *logfile_name)
  74 {
  75         FILE *logfile;
  76
  77         assert(logfile_name);
  78         logfile = fopen(logfile_name, "a");
  79         if (!logfile) {
  80                 DSS_EMERG_LOG("can not open %s: %s\n", logfile_name,
  81                         strerror(errno));
  82                 exit(EXIT_FAILURE);
  83         }
  84         setlinebuf(logfile);
  85         return logfile;
  86 }
  87
  88 /**
  89  * Close the log file of the daemon.
  90  *
  91  * \param logfile The log file handle.
  92  *
  93  * It's OK to call this with logfile == \p NULL.
  94  */
  95 void close_log(FILE* logfile)
  96 {
  97         if (!logfile)
  98                 return;
  99         DSS_INFO_LOG("closing logfile\n");
 100         fclose(logfile);
 101 }
 102
 103 /**
 104  * Log the startup message.
 105  */
 106 void log_welcome(int loglevel)
 107 {
 108         DSS_INFO_LOG("***** welcome to dss ******\n");
 109         DSS_DEBUG_LOG("using loglevel %d\n", loglevel);
 110 }