Add an optional daemon mode

rx.c

@@ -162,9 +162,10 @@ static void usage(FILE *fd)
 	fprintf(fd, "  -c <n>      Number of channels (default %d)\n",
 		DEFAULT_CHANNELS);
 
-	fprintf(fd, "\nDisplay parameters:\n");
+	fprintf(fd, "\nProgram parameters:\n");
 	fprintf(fd, "  -v <n>      Verbosity level (default %d)\n",
 		DEFAULT_VERBOSE);
+	fprintf(fd, "  -D <file>   Run as a daemon, writing process ID to the given file\n");
 }
 
 int main(int argc, char *argv[])
@@ -176,7 +177,8 @@ int main(int argc, char *argv[])
 
 	/* command-line options */
 	const char *device = DEFAULT_DEVICE,
-		*addr = DEFAULT_ADDR;
+		*addr = DEFAULT_ADDR,
+		*pid = NULL;
 	unsigned int buffer = DEFAULT_BUFFER,
 		rate = DEFAULT_RATE,
 		jitter = DEFAULT_JITTER,
@@ -216,6 +218,9 @@ int main(int argc, char *argv[])
 		case 'v':
 			verbose = atoi(optarg);
 			break;
+		case 'D':
+			pid = optarg;
+			break;
 		default:
 			usage(stderr);
 			return -1;
@@ -244,6 +249,9 @@ int main(int argc, char *argv[])
 	if (set_alsa_sw(snd) == -1)
 		return -1;
 
+	if (pid)
+		go_daemon(pid);
+
 	go_realtime();
 	r = run_rx(session, decoder, snd, channels, rate);
 

sched.c

@@ -19,6 +19,7 @@
 
 #include <sched.h>
 #include <stdio.h>
+#include <unistd.h>
 
 #include "sched.h"
 
@@ -49,3 +50,31 @@ int go_realtime(void)
 
 	return 0;
 }
+
+int go_daemon(const char *pid_file)
+{
+	FILE *f;
+
+	if (daemon(0, 0) == -1) {
+		perror("daemon");
+		return -1;
+	}
+
+	if (!pid_file)
+		return 0;
+
+	f = fopen(pid_file, "w");
+	if (!f) {
+		perror("fopen");
+		return -1;
+	}
+
+	fprintf(f, "%d", getpid());
+
+	if (fclose(f) != 0) {
+		perror("fclose");
+		return -1;
+	}
+
+	return 0;
+}

sched.h

@@ -21,5 +21,6 @@
 #define MISC_H
 
 int go_realtime(void);
+int go_daemon(const char *pid_file);
 
 #endif

tx.c

@@ -149,9 +149,10 @@ static void usage(FILE *fd)
 	fprintf(fd, "  -b <kbps>   Bitrate (approx., default %d)\n",
 		DEFAULT_BITRATE);
 
-	fprintf(fd, "\nDisplay parameters:\n");
+	fprintf(fd, "\nProgram parameters:\n");
 	fprintf(fd, "  -v <n>      Verbosity level (default %d)\n",
 		DEFAULT_VERBOSE);
+	fprintf(fd, "  -D <file>   Run as a daemon, writing process ID to the given file\n");
 
 	fprintf(fd, "\nAllowed frame sizes (-f) are defined by the Opus codec. For example,\n"
 		"at 48000Hz the permitted values are 120, 240, 480 or 960.\n");
@@ -168,7 +169,8 @@ int main(int argc, char *argv[])
 
 	/* command-line options */
 	const char *device = DEFAULT_DEVICE,
-		*addr = DEFAULT_ADDR;
+		*addr = DEFAULT_ADDR,
+		*pid = NULL;
 	unsigned int buffer = DEFAULT_BUFFER,
 		rate = DEFAULT_RATE,
 		channels = DEFAULT_CHANNELS,
@@ -181,7 +183,7 @@ int main(int argc, char *argv[])
 	for (;;) {
 		int c;
 
-		c = getopt(argc, argv, "b:c:d:f:h:m:p:r:v:");
+		c = getopt(argc, argv, "b:c:d:f:h:m:p:r:v:D:");
 		if (c == -1)
 			break;
 
@@ -213,6 +215,9 @@ int main(int argc, char *argv[])
 		case 'v':
 			verbose = atoi(optarg);
 			break;
+		case 'D':
+			pid = optarg;
+			break;
 		default:
 			usage(stderr);
 			return -1;
@@ -249,6 +254,9 @@ int main(int argc, char *argv[])
 	if (set_alsa_sw(snd) == -1)
 		return -1;
 
+	if (pid)
+		go_daemon(pid);
+
 	go_realtime();
 	r = run_tx(snd, channels, frame, encoder, bytes_per_frame,
 		ts_per_frame, session);