daemonize module

ccan/daemonize/_info.c

+#include <stdio.h>
+#include <string.h>
+#include "config.h"
+
+/**
+ * daemonize - routine to turn a process into a well-behaved daemon.
+ *
+ * Daemons should detach themselves thoroughly from the process which launched
+ * them, and not prevent any filesystems from being unmounted.  daemonize()
+ * helps with the process.
+ *
+ * Example:
+ *	#include <ccan/daemonize/daemonize.h>
+ *	#include <ccan/str/str.h>
+ *	#include <err.h>
+ *	#include <unistd.h>
+ *	#include <stdlib.h>
+ *	
+ *	static void usage(const char *name)
+ *	{
+ *		errx(1, "Usage: %s [--daemonize]\n", name);
+ *	}
+ *	
+ *	// Wait for a minute, possibly as a daemon.
+ *	int main(int argc, char *argv[])
+ *	{
+ *		if (argc != 1) {
+ *			if (argc == 2 && streq(argv[1], "--daemonize")) {
+ *				if (!daemonize())
+ *					err(1, "Failed to become daemon");
+ *			} else
+ *				usage(argv[1]);
+ *		}
+ *		sleep(60);
+ *		exit(0);
+ *	}
+ *
+ * Licence: BSD (2 clause, ie. MIT)
+ */
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		return 0;
+	}
+
+	if (strcmp(argv[1], "libs") == 0) {
+		return 0;
+	}
+
+	return 1;
+}

ccan/daemonize/daemonize.c

+#include <ccan/daemonize/daemonize.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+/* This code is based on Stevens Advanced Programming in the UNIX
+ * Environment. */
+bool daemonize(void)
+{
+	pid_t pid;
+
+	/* Separate from our parent via fork, so init inherits us. */
+	if ((pid = fork()) < 0)
+		return false;
+	if (pid != 0)
+		exit(0);
+
+	/* Don't hold files open. */
+	close(STDIN_FILENO);
+	close(STDOUT_FILENO);
+	close(STDERR_FILENO);
+
+	/* Session leader so ^C doesn't whack us. */
+	setsid();
+	/* Move off any mount points we might be in. */
+	chdir("/");
+	/* Discard our parent's old-fashioned umask prejudices. */
+	umask(0);
+	return true;
+}

ccan/daemonize/daemonize.h

+#ifndef CCAN_DAEMONIZE_H
+#define CCAN_DAEMONIZE_H
+#include <stdbool.h>
+
+/**
+ * daemonize - turn this process into a daemon.
+ *
+ * This routine forks us off to become a daemon.  It returns false on failure
+ * (ie. fork() failed) and sets errno.
+ *
+ * Side effects for programmers to be aware of:
+ *  - PID changes (our parent exits, we become child of init)
+ *  - stdin, stdout and stderr file descriptors are closed
+ *  - Current working directory changes to /
+ *  - Umask is set to 0.
+ */
+bool daemonize(void);
+
+#endif /* CCAN_DAEMONIZE_H */