Add documentation for using bash script as server command

docs/command_bash.md

@@ -0,0 +1,41 @@
+# Use bash script to start server
+
+You may use a `bash` script to start your server, rather than invoking `java`
+directly. This requires some changes though, to ensure your server properly
+shuts down.
+
+When `lazymc` wants to stop your server, it sends a [`SIGTERM`][sigterm] signal
+to the server command to gracefully shut it down. `bash` ignores this signal by
+default and keeps the server running.
+
+You must configure `bash` to [forward][forward-signal] the signal to properly
+shutdown the Minecraft server as well.
+
+[sigterm]: https://en.wikipedia.org/wiki/Signal_(IPC)#SIGTERM
+[forward-signal]: https://unix.stackexchange.com/a/434269/61092
+
+## Example
+
+Here's a minimal example, trapping the signal and forwarding it to the server.
+Be sure to set the correct server JAR file and appropriate memory limits.
+
+[`start-server`](../res/start-server):
+
+```bash
+#!/bin/bash
+
+# Server JAR file, set this to your own
+FILE=server.jar
+
+# Trap SIGTERM, forward it to server process ID
+trap 'kill -TERM $PID' TERM INT
+
+# Start server
+java -Xms1G -Xmx1G -jar $FILE --nogui &
+
+# Remember server process ID, wait for it to quit, then reset the trap
+PID=$!
+wait $PID
+trap - TERM INT
+wait $PID
+```

res/lazymc.toml

@@ -12,6 +12,8 @@ address = "0.0.0.0:25565"
 directory = "."
 
 # Command to start the server.
+#
+# Warning: if using a bash script, see: https://github.com/timvisee/lazymc/blob/master/docs/command_bash.md
 command = "java -Xmx1G -Xms1G -jar server.jar --nogui"
 
 # Ingress address.
@@ -40,5 +42,5 @@ motd_starting = "§2☻ Server is starting...\n§7⌛ Please wait..."
 login_starting = "Server is starting... §c♥§r\n\nThis may take some time.\n\nPlease try to reconnect in a minute."
 
 [advanced]
-# Automatically set internal IP and port in Minecraft server.properties file.
+# Automatically set IP and port in Minecraft server.properties file.
 rewrite_server_properties = true

res/start-server

@@ -1,19 +1,15 @@
 #!/bin/bash
 
-# Server file
+# Server JAR file, set this to your own
 FILE=server.jar
 
-# Switch to script directory
-DIR="$(dirname "$(realpath "$0")")"
-cd $DIR
-
-# Catch SIGTERM to gracefully stop server
+# Trap SIGTERM, forward it to server process ID
 trap 'kill -TERM $PID' TERM INT
 
 # Start server
 java -Xms1G -Xmx1G -jar $FILE --nogui &
 
-# Clean up stopped server
+# Remember server process ID, wait for it to quit, then reset the trap
 PID=$!
 wait $PID
 trap - TERM INT