tools/lib/: new helper function for daemonification

- include/daemon.h (daemonize), lib/daemon.c: shed all ties with the
  process' previous surroundings
- lib/Makefile (OBJS): added daemon.o

tools/lib/Makefile

@@ -19,7 +19,7 @@ OBJS_host = atusb.o usbopen.o
 OBJS_ben_jlime = atben.o
 OBJS_ben_openwrt = atben.o
 
-OBJS = atrf.o atnet.o misctxrx.o cwtest.o netio.o $(OBJS_$(TARGET))
+OBJS = atrf.o atnet.o misctxrx.o cwtest.o netio.o daemon.o $(OBJS_$(TARGET))
 
 .PHONY:		all clean spotless
 

tools/lib/daemon.c

@@ -0,0 +1,41 @@
+/*
+ * lib/daemon.c - Helper functions for proper daemonification
+ *
+ * Written 2011 by Werner Almesberger
+ * Copyright 2011 Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "daemon.h"
+
+
+pid_t daemonize(void)
+{
+	pid_t pid;
+	int i;
+
+	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		exit(1);
+	}
+	if (pid)
+		return pid;
+	if (setsid() < 0) {
+		perror("setsid");
+		exit(1);
+	}
+	for (i = 0; i <= 2; i++)
+		(void) close(i);
+	(void) chdir("/");
+	return 0;
+}