Add more logging infrastructure

src/daemonitor/000_TopSource.c

@@ -7,9 +7,11 @@
 
 /* Below are all the includes used throughout the application. */
 #include <errno.h>
+#include <fcntl.h>
 #include <stdio.h>
 #include <getopt.h>
 #include <stdarg.h>
+#include <string.h>
 #include <syslog.h>
 #include <unistd.h>
 #include <sys/types.h>

src/daemonitor/101_log.c

@@ -157,6 +157,48 @@ void log_func_syslog(int level, const char* fmt, ...)
 
 
 
+/* log_destination_set()
+ *  Set `log_func' function pointer.
+ */
+void log_destination_set(enum log_destination_t dest)
+{
+    switch(dest) {
+    case log_destination_stdout:
+        log_func_fd = STDOUT_FILENO;
+        log_func = log_func_file;
+        break;
+
+    case log_destination_stderr:
+        log_func_fd = STDERR_FILENO;
+        log_func = log_func_file;
+        break;
+
+    case log_destination_syslog:
+        log_func = log_func_syslog;
+        break;
+
+    case log_destination_file:
+        /* log_func_fd() must be set by log_destination_set_file() */
+        log_func = log_func_file;
+        break;
+    }
+}
+
+
+
+/* log_destination_set_file()
+ *  Open `filename' for writing, return 0 on success and -1 on error. sets `log_func_fd'.
+ */
+int log_destination_set_file(const char* filename) __attribute__((nonnull,warn_unused_result));
+int log_destination_set_file(const char* filename)
+{
+    log_func_fd = open(filename, O_WRONLY | O_CREAT | O_APPEND, 0666);
+    if(log_func_fd == -1) return -1;
+    return 0;
+}
+
+
+
 /* options for text editors
 kate: replace-trailing-space-save true; space-indent true; tab-width 4;
 vim: expandtab:ts=4:sw=4

src/daemonitor/999_main.c

@@ -7,8 +7,77 @@
 
 
 
-int main(void)
+/* usage()
+ *  Display the usage info.
+ */
+void usage(void)
 {
+    fputs("Usage:\n\n"
+        "    daemonitor [options] -- /path/to/program [args]\n\n"
+        "Valid options:\n"
+        " -h, --help                Display this screen.\n"
+        " -V, --version             Display version number.\n"
+        " -l, --log <dest>          Log file destination, may be one of:\n"
+        "                               SYSLOG - log to syslog (default)\n"
+        "                               STDOUT - log to stdout\n"
+        "                               STDERR - log to stderr\n"
+        "                               file path - log to file\n"
+    "", stderr);
+}
+
+
+
+/* options[]
+ *  The array of long commandline options for getopt(3).
+ */
+struct option options[] = {
+    { "help", no_argument, 0, 'h' },
+    { "version", no_argument, 0, 'V' },
+    { "log", required_argument, 0, 'l' },
+    { 0, 0, 0, 0 }
+};
+
+
+
+/* optstr
+ *  The list of short commandline options for getopt(3). Sorted alphabetically, lowercase first.
+ */
+const char* optstr = "hl:V";
+
+
+
+/* main()
+ *  The program driver. Parses the commandline options, sets up the environment, and starts the
+ *  daemon monitoring process.
+ */
+int main(int argc, char* argv[])
+{
+    const char* log_argument = 0;
+
+    while(1) {
+        switch(getopt_long(argc, argv, optstr, options, 0)) {
+        case -1: goto opts_done;
+        case '?': LOG_ANYWHERE("Invalid commandline options."); return 1;
+        case 'h': usage(); return 1;
+        case 'V': fputs("daemonitor " VERSION "\n", stderr); return 1;
+        case 'l': log_argument = optarg; break;
+        }
+    }
+  opts_done:
+    /* set up logging */
+    if(!log_argument || !strcmp(log_argument, "SYSLOG")) {
+        log_destination_set(log_destination_syslog);
+    } else if(!strcmp(log_argument, "STDOUT")) {
+        log_destination_set(log_destination_stdout);
+    } else if(!strcmp(log_argument, "STDERR")) {
+        log_destination_set(log_destination_stderr);
+    } else {
+        if(log_destination_set_file(log_argument)) {
+            LOG_ANYWHERE("Error logging to file `%s' (%m).", log_argument);
+            return 1;
+        }
+    }
+
     return 0;
 }