From ce77b148d927c3012d04f629266476c8ffeb183a Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Fri, 5 Nov 2021 08:48:19 +0100
Subject: [PATCH] CommandLine: add option --systemd

This way, MPD can reliably detect whether it was started as systemd
service, which is better than checking sd_booted(), which only checks
whether systemd manages all services, but still MPD could be started
manually.
---
 src/CommandLine.cxx           | 13 +++++++++++++
 src/CommandLine.hxx           |  5 +++++
 systemd/system/mpd.service.in |  2 +-
 systemd/user/mpd.service.in   |  2 +-
 4 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/CommandLine.cxx b/src/CommandLine.cxx
index e046d5ca4..eb47df39b 100644
--- a/src/CommandLine.cxx
+++ b/src/CommandLine.cxx
@@ -86,6 +86,9 @@ enum Option {
 	OPTION_KILL,
 	OPTION_NO_CONFIG,
 	OPTION_NO_DAEMON,
+#ifdef __linux__
+	OPTION_SYSTEMD,
+#endif
 	OPTION_STDOUT,
 	OPTION_STDERR,
 	OPTION_VERBOSE,
@@ -98,6 +101,9 @@ static constexpr OptionDef option_defs[] = {
 	{"kill", "kill the currently running mpd session"},
 	{"no-config", "don't read from config"},
 	{"no-daemon", "don't detach from console"},
+#ifdef __linux__
+	{"systemd", "systemd service mode"},
+#endif
 	{"stdout", nullptr}, // hidden, compatibility with old versions
 	{"stderr", "print messages to stderr"},
 	{"verbose", 'v', "verbose logging"},
@@ -349,6 +355,13 @@ ParseCommandLine(int argc, char **argv, struct options &options,
 			options.daemon = false;
 			break;
 
+#ifdef __linux__
+		case OPTION_SYSTEMD:
+			options.daemon = false;
+			options.systemd = true;
+			break;
+#endif
+
 		case OPTION_STDOUT:
 		case OPTION_STDERR:
 			options.log_stderr = true;
diff --git a/src/CommandLine.hxx b/src/CommandLine.hxx
index b7f48e926..744341299 100644
--- a/src/CommandLine.hxx
+++ b/src/CommandLine.hxx
@@ -25,6 +25,11 @@ struct ConfigData;
 struct options {
 	bool kill = false;
 	bool daemon = true;
+
+#ifdef __linux__
+	bool systemd = false;
+#endif
+
 	bool log_stderr = false;
 	bool verbose = false;
 };
diff --git a/systemd/system/mpd.service.in b/systemd/system/mpd.service.in
index c54954246..e0707507d 100644
--- a/systemd/system/mpd.service.in
+++ b/systemd/system/mpd.service.in
@@ -5,7 +5,7 @@ After=network.target sound.target
 
 [Service]
 Type=notify
-ExecStart=@prefix@/bin/mpd --no-daemon
+ExecStart=@prefix@/bin/mpd --systemd
 
 # Create /run/mpd (if MPD is launched without the socket unit and is
 # configured to bind listener sockets there).
diff --git a/systemd/user/mpd.service.in b/systemd/user/mpd.service.in
index 8b5a39fd4..6f8474e02 100644
--- a/systemd/user/mpd.service.in
+++ b/systemd/user/mpd.service.in
@@ -5,7 +5,7 @@ After=network.target sound.target
 
 [Service]
 Type=notify
-ExecStart=@prefix@/bin/mpd --no-daemon
+ExecStart=@prefix@/bin/mpd --systemd
 
 # Create /run/user/$UID/mpd (if MPD is launched without the socket
 # unit and is configured to bind listener sockets there).