Allow x52d to daemonize

Prior to this change, x52d could only run in the foreground, regardless
of the value of the foreground flag. This change adds the standard
double-fork routine to daemonize the program.

This change also adds a PID file argument to x52d, which is used to
ensure that only one instance of the x52d daemon is running at any time.

daemon/x52d_const.h

@@ -15,6 +15,8 @@
 
 #define X52D_SYS_CFG_FILE   SYSCONFDIR "/" X52D_APP_NAME "/" X52D_APP_NAME ".conf"
 
+#define X52D_PID_FILE   RUNDIR "/" X52D_APP_NAME ".pid"
+
 #include "gettext.h"
 #define N_(x) gettext_noop(x)
 #define _(x) gettext(x)

daemon/x52d_main.c

@@ -10,6 +10,8 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 #include <signal.h>
 #include <unistd.h>
 #include <errno.h>
@@ -74,11 +76,115 @@ __attribute__((noreturn))
 static void usage(int exit_code)
 {
     fprintf(stderr,
-            _("Usage: %s [-f] [-v] [-q] [-l log-file] [-o override] [-c config-file]\n"),
+            _("Usage: %s [-f] [-v] [-q]\n"
+              "\t[-l log-file] [-o override]\n"
+              "\t[-c config-file] [-p pid-file]\n"),
             X52D_APP_NAME);
     exit(exit_code);
 }
 
+static void start_daemon(bool foreground, const char *pid_file)
+{
+    pid_t pid;
+    FILE *pid_fd;
+
+    if (pid_file == NULL) {
+        pid_file = X52D_PID_FILE;
+    }
+
+    /* Check if there is an existing daemon process running */
+    pid_fd = fopen(pid_file, "r");
+    if (pid_fd != NULL) {
+        int rc;
+
+        /* File exists, read the PID and check if it exists */
+        rc = fscanf(pid_fd, "%u", &pid);
+        fclose(pid_fd);
+
+        if (rc != 1) {
+            perror("fscanf");
+        } else {
+            rc = kill(pid, 0);
+            if (rc == 0 || (rc < 0 && errno == EPERM)) {
+                PINELOG_FATAL(_("Daemon is already running as PID %u"), pid);
+            }
+        }
+    }
+
+    if (!foreground) {
+        /* Fork off the parent process */
+        pid = fork();
+        if (pid < 0) {
+            /* Error occurred during first fork */
+            perror("fork");
+            exit(EXIT_FAILURE);
+        } else if (pid > 0) {
+            /* Terminate the parent process */
+            exit(EXIT_SUCCESS);
+        }
+
+        /* Make child process a session leader */
+        if (setsid() < 0) {
+            perror("setsid");
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    /* Initialize signal handlers. This step is the same whether in foreground
+     * or background mode
+     */
+    listen_signal(SIGINT, termination_handler);
+    listen_signal(SIGTERM, termination_handler);
+    listen_signal(SIGQUIT, termination_handler);
+    listen_signal(SIGHUP, reload_handler);
+
+    if (!foreground) {
+        /* Fork off for the second time */
+        pid = fork();
+        if (pid < 0) {
+            /* Error occurred during second fork */
+            perror("fork");
+            exit(EXIT_FAILURE);
+        } else if (pid > 0) {
+            /* Terminate the parent */
+            exit(EXIT_SUCCESS);
+        }
+    }
+
+    /* Write the PID to the pid_file */
+    pid_fd = fopen(pid_file, "w");
+    if (pid_fd == NULL) {
+        /* Unable to open PID file */
+        perror("fopen");
+        exit(EXIT_FAILURE);
+    }
+    if (fprintf(pid_fd, "%u\n", getpid()) < 0) {
+        perror("fprintf");
+        exit(EXIT_FAILURE);
+    }
+    if (fclose(pid_fd) != 0) {
+        perror("fclose");
+        exit(EXIT_FAILURE);
+    }
+
+    if (!foreground) {
+        /* Set new file permissions */
+        umask(0);
+
+        /* Change the working directory */
+        if (chdir("/")) {
+            /* Error changing the directory */
+            perror("chdir");
+            exit(EXIT_FAILURE);
+        }
+
+        /* Close all open file descriptors */
+        for (int x = sysconf(_SC_OPEN_MAX); x >= 0; x--) {
+            close(x);
+        }
+    }
+}
+
 int main(int argc, char **argv)
 {
     int verbosity = 0;
@@ -86,6 +192,7 @@ int main(int argc, char **argv)
     bool foreground = false;
     char *log_file = NULL;
     char *conf_file = NULL;
+    const char *pid_file = NULL;
     int opt;
 
     /* Initialize gettext */
@@ -107,8 +214,9 @@ int main(int argc, char **argv)
      * -v   verbose logging
      * -q   silent behavior
      * -l   path to log file
+     * -p   path to PID file (only used if running in background)
      */
-    while ((opt = getopt(argc, argv, "fvql:o:c:h")) != -1) {
+    while ((opt = getopt(argc, argv, "fvql:o:c:p:h")) != -1) {
         switch (opt) {
         case 'f':
             foreground = true;
@@ -145,6 +253,10 @@ int main(int argc, char **argv)
             conf_file = optarg;
             break;
 
+        case 'p':
+            pid_file = optarg;
+            break;
+
         case 'h':
             usage(EXIT_SUCCESS);
             break;
@@ -161,15 +273,16 @@ int main(int argc, char **argv)
     PINELOG_DEBUG(_("Log file = %s"), log_file);
     PINELOG_DEBUG(_("Config file = %s"), conf_file);
 
+    /* Set default PID file */
+    if (pid_file == NULL) {
+        pid_file = X52D_PID_FILE;
+    }
+
+    start_daemon(foreground, pid_file);
+
     set_log_file(foreground, log_file);
     x52d_config_load(conf_file);
 
-    // Initialize signal handlers
-    listen_signal(SIGINT, termination_handler);
-    listen_signal(SIGTERM, termination_handler);
-    listen_signal(SIGQUIT, termination_handler);
-    listen_signal(SIGHUP, reload_handler);
-
     // Start device threads
     x52d_dev_init();
     x52d_clock_init();
@@ -192,9 +305,16 @@ int main(int argc, char **argv)
         }
     }
 
+    PINELOG_INFO(_("Received termination signal %s"), strsignal(flag_quit));
+
     // Stop device threads
     x52d_clock_exit();
     x52d_dev_exit();
+
+    // Remove the PID file
+    PINELOG_TRACE("Removing PID file %s", pid_file);
+    unlink(pid_file);
+
     PINELOG_INFO(_("Shutting down X52 daemon"));
 
     return 0;

po/x52pro-linux.pot

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: x52pro-linux 0.2.2\n"
 "Report-Msgid-Bugs-To: https://github.com/nirenjan/x52pro-linux/issues\n"
-"POT-Creation-Date: 2021-07-29 22:58-0700\n"
+"POT-Creation-Date: 2021-08-04 13:11-0700\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -491,64 +491,77 @@ msgstr ""
 msgid "OK"
 msgstr ""
 
-#: daemon/x52d_main.c:50
+#: daemon/x52d_main.c:52
 #, c-format
 msgid "Error %d setting log file: %s\n"
 msgstr ""
 
-#: daemon/x52d_main.c:66
+#: daemon/x52d_main.c:68
 #, c-format
 msgid "Error %d installing handler for signal %d: %s"
 msgstr ""
 
-#: daemon/x52d_main.c:77
+#: daemon/x52d_main.c:79
 #, c-format
-msgid "Usage: %s [-f] [-v] [-q] [-l log-file] [-o override] [-c config-file]\n"
+msgid ""
+"Usage: %s [-f] [-v] [-q]\n"
+"\t[-l log-file] [-o override]\n"
+"\t[-c config-file] [-p pid-file]\n"
 msgstr ""
 
-#: daemon/x52d_main.c:138
+#: daemon/x52d_main.c:109
+#, c-format
+msgid "Daemon is already running as PID %u"
+msgstr ""
+
+#: daemon/x52d_main.c:246
 #, c-format
 msgid "Unable to parse configuration override '%s'\n"
 msgstr ""
 
-#: daemon/x52d_main.c:158
+#: daemon/x52d_main.c:270
 #, c-format
 msgid "Foreground = %s"
 msgstr ""
 
-#: daemon/x52d_main.c:158 daemon/x52d_main.c:159
+#: daemon/x52d_main.c:270 daemon/x52d_main.c:271
 msgid "true"
 msgstr ""
 
-#: daemon/x52d_main.c:158 daemon/x52d_main.c:159
+#: daemon/x52d_main.c:270 daemon/x52d_main.c:271
 msgid "false"
 msgstr ""
 
-#: daemon/x52d_main.c:159
+#: daemon/x52d_main.c:271
 #, c-format
 msgid "Quiet = %s"
 msgstr ""
 
-#: daemon/x52d_main.c:160
+#: daemon/x52d_main.c:272
 #, c-format
 msgid "Verbosity = %d"
 msgstr ""
 
-#: daemon/x52d_main.c:161
+#: daemon/x52d_main.c:273
 #, c-format
 msgid "Log file = %s"
 msgstr ""
 
-#: daemon/x52d_main.c:162
+#: daemon/x52d_main.c:274
 #, c-format
 msgid "Config file = %s"
 msgstr ""
 
-#: daemon/x52d_main.c:188
+#: daemon/x52d_main.c:301
 msgid "Reloading X52 configuration"
 msgstr ""
 
-#: daemon/x52d_main.c:198
+#: daemon/x52d_main.c:308
+#, c-format
+msgid "Received termination signal %s"
+msgstr ""
+
+#: daemon/x52d_main.c:318
 msgid "Shutting down X52 daemon"
 msgstr ""
 
@@ -557,7 +570,7 @@ msgstr ""
 msgid "Setting clock enable to %s"
 msgstr ""
 
-#: daemon/x52d_clock.c:34 daemon/x52d_clock.c:112
+#: daemon/x52d_clock.c:34 daemon/x52d_clock.c:113
 #, c-format
 msgid "Setting %s clock timezone to %s"
 msgstr ""
@@ -570,39 +583,39 @@ msgstr ""
 msgid "UTC"
 msgstr ""
 
-#: daemon/x52d_clock.c:53
+#: daemon/x52d_clock.c:54
 msgid "Unable to allocate memory for timezone. Falling back to UTC"
 msgstr ""
 
-#: daemon/x52d_clock.c:63
+#: daemon/x52d_clock.c:64
 msgid "Unable to backup timezone environment. Falling back to UTC"
 msgstr ""
 
-#: daemon/x52d_clock.c:129
+#: daemon/x52d_clock.c:130
 #, c-format
 msgid "Setting %s clock format to %s"
 msgstr ""
 
-#: daemon/x52d_clock.c:151
+#: daemon/x52d_clock.c:152
 #, c-format
 msgid "Setting date format to %s"
 msgstr ""
 
-#: daemon/x52d_clock.c:161
+#: daemon/x52d_clock.c:162
 msgid "Starting X52 clock manager thread"
 msgstr ""
 
-#: daemon/x52d_clock.c:172
+#: daemon/x52d_clock.c:173
 #, c-format
 msgid "Error %d retrieving current time: %s"
 msgstr ""
 
-#: daemon/x52d_clock.c:193
+#: daemon/x52d_clock.c:194
 #, c-format
 msgid "Error %d initializing clock thread: %s"
 msgstr ""
 
-#: daemon/x52d_clock.c:200
+#: daemon/x52d_clock.c:201
 msgid "Shutting down X52 clock manager thread"
 msgstr ""
 

po/xx_PL.po

@@ -7,8 +7,8 @@ msgid ""
 msgstr ""
 "Project-Id-Version: x52pro-linux 0.2.1\n"
 "Report-Msgid-Bugs-To: https://github.com/nirenjan/x52pro-linux/issues\n"
-"POT-Creation-Date: 2021-07-29 22:58-0700\n"
+"POT-Creation-Date: 2021-08-04 13:11-0700\n"
-"PO-Revision-Date: 2021-07-27 02:08-0700\n"
+"PO-Revision-Date: 2021-08-04 13:12-0700\n"
 "Last-Translator: Nirenjan Krishnan <nirenjan@gmail.com>\n"
 "Language-Team: Dummy Language for testing i18n\n"
 "Language: xx_PL\n"
@@ -534,66 +534,80 @@ msgstr "Estingtay aracterchay 0x%02x..."
 msgid "OK"
 msgstr "OKay"
 
-#: daemon/x52d_main.c:50
+#: daemon/x52d_main.c:52
 #, c-format
 msgid "Error %d setting log file: %s\n"
 msgstr "Erroray %d ettingsay oglay ilefay: %s\n"
 
-#: daemon/x52d_main.c:66
+#: daemon/x52d_main.c:68
 #, c-format
 msgid "Error %d installing handler for signal %d: %s"
 msgstr "Erroray %d installingay andlerhay orfay ignalsay %d: %s"
 
-#: daemon/x52d_main.c:77
+#: daemon/x52d_main.c:79
 #, c-format
-msgid "Usage: %s [-f] [-v] [-q] [-l log-file] [-o override] [-c config-file]\n"
+msgid ""
+"Usage: %s [-f] [-v] [-q]\n"
+"\t[-l log-file] [-o override]\n"
+"\t[-c config-file] [-p pid-file]\n"
 msgstr ""
-"Usageay: %s [-f] [-v] [-q] [-l oglay-ilefay] [-o overrideay] [-c onfigcay-"
+"Usageay: %s [-f] [-v] [-q]\n"
-"ilefay]\n"
+"\t[-l oglay-ilefay] [-o overrideay]\n"
+"\t[-c onfigcay-ilefay] [-p idpay-ilefay]\n"
 
-#: daemon/x52d_main.c:138
+#: daemon/x52d_main.c:109
+#, c-format
+msgid "Daemon is already running as PID %u"
+msgstr "Aemonday isay alreadyay unningray asay IDPay %u"
+
+#: daemon/x52d_main.c:246
 #, c-format
 msgid "Unable to parse configuration override '%s'\n"
 msgstr "Unableay otay arsepay onfigurationcay overrideay '%s'\n"
 
-#: daemon/x52d_main.c:158
+#: daemon/x52d_main.c:270
 #, c-format
 msgid "Foreground = %s"
 msgstr "Oregroundfay = %s"
 
-#: daemon/x52d_main.c:158 daemon/x52d_main.c:159
+#: daemon/x52d_main.c:270 daemon/x52d_main.c:271
 msgid "true"
 msgstr "uetray"
 
-#: daemon/x52d_main.c:158 daemon/x52d_main.c:159
+#: daemon/x52d_main.c:270 daemon/x52d_main.c:271
 msgid "false"
 msgstr "alsefay"
 
-#: daemon/x52d_main.c:159
+#: daemon/x52d_main.c:271
 #, c-format
 msgid "Quiet = %s"
 msgstr "Uietqay = %s"
 
-#: daemon/x52d_main.c:160
+#: daemon/x52d_main.c:272
 #, c-format
 msgid "Verbosity = %d"
 msgstr "Erbosityvay = %d"
 
-#: daemon/x52d_main.c:161
+#: daemon/x52d_main.c:273
 #, c-format
 msgid "Log file = %s"
 msgstr "Oglay ilefay = %s"
 
-#: daemon/x52d_main.c:162
+#: daemon/x52d_main.c:274
 #, c-format
 msgid "Config file = %s"
 msgstr "Onfigcay ilefay = %s"
 
-#: daemon/x52d_main.c:188
+#: daemon/x52d_main.c:301
 msgid "Reloading X52 configuration"
 msgstr "Eloadingray X52 onfigurationcay"
 
-#: daemon/x52d_main.c:198
+#: daemon/x52d_main.c:308
+#, c-format
+msgid "Received termination signal %s"
+msgstr "Eceivedray erminationtay ignalsay %s"
+
+#: daemon/x52d_main.c:318
 msgid "Shutting down X52 daemon"
 msgstr "Uttingshay ownday X52 aemonday"
 
@@ -602,7 +616,7 @@ msgstr "Uttingshay ownday X52 aemonday"
 msgid "Setting clock enable to %s"
 msgstr "Ettingsay ockclay enableay otay %s"
 
-#: daemon/x52d_clock.c:34 daemon/x52d_clock.c:112
+#: daemon/x52d_clock.c:34 daemon/x52d_clock.c:113
 #, c-format
 msgid "Setting %s clock timezone to %s"
 msgstr "Ettingsay %s ockclay imezonetay otay %s"
@@ -615,42 +629,42 @@ msgstr "ocallay"
 msgid "UTC"
 msgstr "UTCay"
 
-#: daemon/x52d_clock.c:53
+#: daemon/x52d_clock.c:54
 msgid "Unable to allocate memory for timezone. Falling back to UTC"
 msgstr ""
 "Unableay otay allocateay emorymay orfay imezonetay. Allingfay ackbay otay "
 "UTCay"
 
-#: daemon/x52d_clock.c:63
+#: daemon/x52d_clock.c:64
 msgid "Unable to backup timezone environment. Falling back to UTC"
 msgstr ""
 "Unableay otay ackupbay imezonetay environmentay. Allingfay ackbay otay UTCay"
 
-#: daemon/x52d_clock.c:129
+#: daemon/x52d_clock.c:130
 #, c-format
 msgid "Setting %s clock format to %s"
 msgstr "Ettingsay %s ockclay ormatfay otay %s"
 
-#: daemon/x52d_clock.c:151
+#: daemon/x52d_clock.c:152
 #, c-format
 msgid "Setting date format to %s"
 msgstr "Ettingsay ateday ormatfay otay %s"
 
-#: daemon/x52d_clock.c:161
+#: daemon/x52d_clock.c:162
 msgid "Starting X52 clock manager thread"
 msgstr "Artingstay X52 ockclay anagermay eadthray"
 
-#: daemon/x52d_clock.c:172
+#: daemon/x52d_clock.c:173
 #, c-format
 msgid "Error %d retrieving current time: %s"
 msgstr "Erroray %d etrievingray urrentcay imetay: %s"
 
-#: daemon/x52d_clock.c:193
+#: daemon/x52d_clock.c:194
 #, c-format
 msgid "Error %d initializing clock thread: %s"
 msgstr "Erroray %d initializingay ockclay eadthray: %s"
 
-#: daemon/x52d_clock.c:200
+#: daemon/x52d_clock.c:201
 msgid "Shutting down X52 clock manager thread"
 msgstr "Uttingshay ownday X52 ockclay anagermay eadthray"