added utils module to share some code parts with other apps

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>

utils.c

@@ -0,0 +1,111 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#include "utils.h"
+
+typedef char pid_str[16];
+
+static int daemonize = 0;
+
+void daemonize_enable(void)
+{
+    daemonize = 1;
+}
+
+static int is_daemon_running(char const * const pidfile, pid_str ps)
+{
+    int pfd = open(pidfile, O_RDONLY, 0);
+    char proc_path[32];
+
+    if (pfd < 0)
+    {
+        return 0;
+    }
+
+    if (read(pfd, ps, sizeof(pid_str)) <= 0)
+    {
+        return 1;
+    }
+
+    close(pfd);
+
+    if (snprintf(proc_path, sizeof(pid_str), "/proc/%s", ps) <= 0)
+    {
+        return 1;
+    }
+
+    if (access(proc_path, F_OK) == 0)
+    {
+        return 1;
+    }
+
+    return 0;
+}
+
+static int create_pidfile(char const * const pidfile)
+{
+    int pfd;
+
+    pfd = open(pidfile, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+
+    if (pfd < 0)
+    {
+        syslog(LOG_DAEMON | LOG_ERR, "Could open pidfile %s for writing: %s", pidfile, strerror(errno));
+        return 1;
+    }
+
+    if (dprintf(pfd, "%d", getpid()) <= 0)
+    {
+        close(pfd);
+        return 1;
+    }
+
+    close(pfd);
+
+    return 0;
+}
+
+int daemonize_with_pidfile(char const * const pidfile)
+{
+    pid_str ps;
+
+    if (daemonize != 0)
+    {
+        if (is_daemon_running(pidfile, ps) != 0)
+        {
+            syslog(LOG_DAEMON | LOG_ERR, "Pidfile %s found and daemon %s still running", pidfile, ps);
+            return 1;
+        }
+
+        if (daemon(0, 0) != 0)
+        {
+            syslog(LOG_DAEMON | LOG_ERR, "daemon: %s", strerror(errno));
+            return 1;
+        }
+
+        if (create_pidfile(pidfile) != 0)
+        {
+            return 1;
+        }
+    }
+
+    return 0;
+}
+
+int daemonize_shutdown(char const * const pidfile)
+{
+    if (daemonize != 0)
+    {
+        if (unlink(pidfile) != 0)
+        {
+            syslog(LOG_DAEMON | LOG_ERR, "Could not unlink pidfile %s: %s", pidfile, strerror(errno));
+            return 1;
+        }
+    }
+
+    return 0;
+}