made log target a commandline option

src/cfgfile.c

@@ -66,9 +66,6 @@ void default_cfg(struct cfg *cfg)
 		cfg->devname[i] = 0;
 		cfg->devid[i][0] = cfg->devid[i][1] = -1;
 	}
-
-	cfg->use_logfile = 1;
-	cfg->use_syslog = 1;
 }
 
 #define EXPECT(cond) \
@@ -315,13 +312,6 @@ int read_cfg(const char *fname, struct cfg *cfg)
 				continue;
 			}
 
-		} else if(strcmp(key_str, "logfile") == 0) {
-			strncpy(cfg->logfile, val_str, PATH_MAX - 1);
-
-		} else if(strcmp(key_str, "log") == 0) {
-			cfg->use_logfile = strstr(val_str, "file") == 0 ? 1 : 0;
-			cfg->use_syslog = strstr(val_str, "syslog") == 0 ? 1 : 0;
-
 		} else {
 			logmsg(LOG_WARNING, "unrecognized config option: %s\n", key_str);
 		}
@@ -473,33 +463,6 @@ int write_cfg(const char *fname, struct cfg *cfg)
 	}
 	fprintf(fp, "\n");
 
-	fprintf(fp, "# Log file path\n");
-	if(cfg->logfile[0]) {
-		fprintf(fp, "logfile = %s\n\n", cfg->logfile);
-	} else {
-		fprintf(fp, "#logfile = " DEF_LOGFILE "\n\n");
-	}
-
-	fprintf(fp, "# Log targets\n");
-	fprintf(fp, "#\n");
-	fprintf(fp, "# Valid options are:\n");
-	fprintf(fp, "#  - file: log messages to a file defined by the logfile option.\n");
-	fprintf(fp, "#  - syslog: log messages to the system logging daemon.\n");
-	fprintf(fp, "#  Combine multiple options by listing them on the same line.\n");
-	fprintf(fp, "#\n");
-	if(cfg->use_logfile || cfg->use_syslog) {
-		fprintf(fp, "log =");
-		if(cfg->use_logfile) {
-			fprintf(fp, " file");
-		}
-		if(cfg->use_syslog) {
-			fprintf(fp, " syslog");
-		}
-		fputc('\n', fp);
-	} else {
-		fprintf(fp, "#log = file, syslog\n");
-	}
-
 	/* unlock */
 	flk.l_type = F_UNLCK;
 	flk.l_start = flk.l_len = 0;

src/cfgfile.h

@@ -1,6 +1,6 @@
 /*
 spacenavd - a free software replacement driver for 6dof space-mice.
-Copyright (C) 2007-2018 John Tsiombikas <nuclear@member.fsf.org>
+Copyright (C) 2007-2019 John Tsiombikas <nuclear@member.fsf.org>
 
 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
@@ -45,9 +45,6 @@ struct cfg {
 
 	char *devname[MAX_CUSTOM];	/* custom USB device name list */
 	int devid[MAX_CUSTOM][2];	/* custom USB vendor/product id list */
-
-	char logfile[PATH_MAX];
-	int use_logfile, use_syslog;
 };
 
 void default_cfg(struct cfg *cfg);

src/dev_usb_linux.c

@@ -311,7 +311,7 @@ struct usb_device_info *find_usb_devices(int (*match)(const struct usb_device_in
 	buf_len = sizeof(buf) - 1;
 	if(!(fp = fopen(PROC_DEV, "r"))) {
 		if(verbose) {
-			logmsg(LOG_ERR, "failed to open " PROC_DEV);
+			logmsg(LOG_ERR, "failed to open " PROC_DEV ": %s\n", strerror(errno));
 		}
 		goto alt_detect;
 	}

src/logger.c

@@ -36,6 +36,7 @@ int start_logfile(const char *fname)
 int start_syslog(const char *id)
 {
 	openlog(id, LOG_NDELAY, LOG_DAEMON);
+	use_syslog = 1;
 	return 0;
 }
 
@@ -43,22 +44,11 @@ void logmsg(int prio, const char *fmt, ...)
 {
 	va_list ap;
 
-	/* if a logfile isn't open, assume we are not daemonized, and try to output
-	 * to stdout/stderr as usual. If we are daemonized but don't have a log file
-	 * this will end up writing harmlessly to /dev/null (see daemonize in spnavd.c)
-	 */
-	va_start(ap, fmt);
 	if(logfile) {
+		va_start(ap, fmt);
 		vfprintf(logfile, fmt, ap);
-	} else {
-		if(prio <= LOG_WARNING) {
-			vfprintf(stderr, fmt, ap);
-		} else {
-			vprintf(fmt, ap);
-		}
+		va_end(ap);
 	}
-	va_end(ap);
-
 	if(use_syslog) {
 		va_start(ap, fmt);
 		vsyslog(prio, fmt, ap);

src/spnavd.c

@@ -45,6 +45,7 @@ static void handle_events(fd_set *rset);
 static void sig_handler(int s);
 
 static const char *cfgfile = DEF_CFGFILE;
+static const char *logfile = DEF_LOGFILE;
 
 int main(int argc, char **argv)
 {
@@ -65,6 +66,18 @@ int main(int argc, char **argv)
 				cfgfile = argv[i];
 				break;
 
+			case 'l':
+				if(!argv[++i]) {
+					fprintf(stderr, "-l must be followed by a logfile name or \"syslog\"\n");
+					return 1;
+				}
+				if(strcmp(argv[i], "syslog") == 0) {
+					logfile = 0;
+				} else {
+					logfile = argv[i];
+				}
+				break;
+
 			case 'v':
 				verbose = 1;
 				break;
@@ -72,10 +85,11 @@ int main(int argc, char **argv)
 			case 'h':
 				printf("usage: %s [options]\n", argv[0]);
 				printf("options:\n");
-				printf(" -d         do not daemonize\n");
-				printf(" -c <file>  config file path (default: " DEF_CFGFILE ")\n");
-				printf(" -v         verbose output\n");
-				printf(" -h         print usage information and exit\n");
+				printf(" -d: do not daemonize\n");
+				printf(" -c <file>: config file path (default: " DEF_CFGFILE ")\n");
+				printf(" -l <file>|syslog: log file path or log to syslog (default: " DEF_LOGFILE ")\n");
+				printf(" -v: verbose output\n");
+				printf(" -h: print usage information and exit\n");
 				return 0;
 
 			default:
@@ -102,15 +116,6 @@ int main(int argc, char **argv)
 
 	read_cfg(cfgfile, &cfg);
 
-	if(become_daemon) {
-		if(cfg.use_syslog) {
-			start_syslog(SYSLOG_ID);
-		}
-		if(cfg.use_logfile) {
-			start_logfile(cfg.logfile[0] ? cfg.logfile : DEF_LOGFILE);
-		}
-	}
-
 	signal(SIGINT, sig_handler);
 	signal(SIGTERM, sig_handler);
 	signal(SIGSEGV, sig_handler);
@@ -250,14 +255,24 @@ static void daemonize(void)
 	setsid();
 	chdir("/");
 
-	/* redirect standard input/output/error */
+	/* redirect standard input/output/error
+	 * best effort attempt to make either the logfile or the syslog socket
+	 * accessible through stdout/stderr, just in case any printfs survived
+	 * the logmsg conversion.
+	 */
 	for(i=0; i<3; i++) {
 		close(i);
 	}
 
 	open("/dev/zero", O_RDONLY);
-	open("/dev/null", O_WRONLY);
+
+	if(!logfile || start_logfile(logfile) == -1) {
+		start_syslog(SYSLOG_ID);
+	}
 	dup(1);
+
+	setvbuf(stdout, 0, _IOLBF, 0);
+	setvbuf(stderr, 0, _IONBF, 0);
 }
 
 static int write_pid_file(void)