Merge commit '474f163b53d438955dae1a0cc9d7df46344b3950' as 'Code/devterm_wiringpi_cpi'

Code/devterm_wiringpi_cpi/wiringPiD/daemonise.c

@@ -0,0 +1,82 @@
+/*
+ * daemonise.c:
+ *	Fairly generic "Turn the current process into a daemon" code.
+ *
+ *	Copyright (c) 2016-2017 Gordon Henderson.
+ *********************************************************************************
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <syslog.h>
+#include <signal.h>
+#include <sys/stat.h>
+
+#include "daemonise.h"
+
+void daemonise (const char *pidFile)
+{
+  pid_t pid ;
+  int i ;
+  FILE *fd ;
+
+  syslog (LOG_DAEMON | LOG_INFO, "Becoming daemon") ;
+
+// Fork from the parent
+
+  if ((pid = fork ()) < 0)
+  {
+    syslog (LOG_DAEMON | LOG_ALERT, "Fork no. 1 failed: %m") ;
+    exit (EXIT_FAILURE) ;
+  }
+
+  if (pid > 0)			// Parent - terminate
+    exit (EXIT_SUCCESS) ;
+
+// Now running on the child - become session leader
+
+  if (setsid() < 0)
+  {
+    syslog (LOG_DAEMON | LOG_ALERT, "setsid failed: %m") ;
+    exit (EXIT_FAILURE) ;
+  }
+
+// Ignore a few signals
+
+  signal (SIGCHLD, SIG_IGN) ;
+  signal (SIGHUP,  SIG_IGN) ;
+
+// Fork again
+
+  if ((pid = fork ()) < 0)
+  {
+    syslog (LOG_DAEMON | LOG_ALERT, "Fork no. 2 failed: %m") ;
+    exit (EXIT_FAILURE) ;
+  }
+
+  if (pid > 0)			// parent - terminate
+    exit (EXIT_SUCCESS) ;
+
+// Tidying up - reset umask, change to / and close all files
+
+  umask (0) ;
+  chdir ("/") ;
+
+  for (i = 0 ; i < sysconf (_SC_OPEN_MAX) ; ++i)
+    close (i) ;
+
+// Write PID into /var/run
+
+  if (pidFile != NULL)
+  {
+    if ((fd = fopen (pidFile, "w")) == NULL)
+    {
+      syslog (LOG_DAEMON | LOG_ALERT, "Unable to write PID file: %m") ;
+      exit (EXIT_FAILURE) ;
+    }
+
+    fprintf (fd, "%d\n", getpid ()) ;
+    fclose (fd) ;
+  }
+}