83 lines
1.6 KiB
C
83 lines
1.6 KiB
C
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/*
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* daemonise.c:
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* Fairly generic "Turn the current process into a daemon" code.
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*
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* Copyright (c) 2016-2017 Gordon Henderson.
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*********************************************************************************
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <syslog.h>
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#include <signal.h>
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#include <sys/stat.h>
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#include "daemonise.h"
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void daemonise (const char *pidFile)
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{
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pid_t pid ;
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int i ;
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FILE *fd ;
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syslog (LOG_DAEMON | LOG_INFO, "Becoming daemon") ;
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// Fork from the parent
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if ((pid = fork ()) < 0)
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{
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syslog (LOG_DAEMON | LOG_ALERT, "Fork no. 1 failed: %m") ;
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exit (EXIT_FAILURE) ;
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}
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if (pid > 0) // Parent - terminate
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exit (EXIT_SUCCESS) ;
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// Now running on the child - become session leader
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if (setsid() < 0)
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{
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syslog (LOG_DAEMON | LOG_ALERT, "setsid failed: %m") ;
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exit (EXIT_FAILURE) ;
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}
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// Ignore a few signals
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signal (SIGCHLD, SIG_IGN) ;
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signal (SIGHUP, SIG_IGN) ;
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// Fork again
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if ((pid = fork ()) < 0)
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{
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syslog (LOG_DAEMON | LOG_ALERT, "Fork no. 2 failed: %m") ;
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exit (EXIT_FAILURE) ;
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}
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if (pid > 0) // parent - terminate
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exit (EXIT_SUCCESS) ;
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// Tidying up - reset umask, change to / and close all files
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umask (0) ;
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chdir ("/") ;
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for (i = 0 ; i < sysconf (_SC_OPEN_MAX) ; ++i)
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close (i) ;
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// Write PID into /var/run
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if (pidFile != NULL)
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{
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if ((fd = fopen (pidFile, "w")) == NULL)
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{
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syslog (LOG_DAEMON | LOG_ALERT, "Unable to write PID file: %m") ;
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exit (EXIT_FAILURE) ;
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}
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fprintf (fd, "%d\n", getpid ()) ;
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fclose (fd) ;
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}
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}
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