cmd/stepd: Write PID file

Closes #9

cmd/stepd/main.go

@@ -17,19 +17,26 @@ import "git.tebibyte.media/sashakoshka/go-service/routines"
 
 func main () {
 	// parse command line arguments
+	flagPidFile := cli.NewInputFlag (
+		'p', "pid-file",
+		"Write the PID to the specified file",
+		"", cli.ValString)
 	flagAddress := cli.NewInputFlag (
 		'a', "address",
 		"The address to host the server on",
 		":8080", cli.ValString)
+	// TODO have in conf, override here
 	flagErrorDocument := cli.NewInputFlag (
 		0, "error-document",
 		"The document to use for displaying errors",
 		"", cli.ValString)
+	// TODO have in conf, override here
 	flagDirectories := cli.NewFlag (
 		'd', "directories",
 		"Serve the contents of directories")
 	cmd := cli.New (
 		"Run an HTTP server that automaticaly executes STEP files",
+		flagPidFile,
 		flagAddress,
 		flagErrorDocument,
 		flagDirectories,
@@ -75,8 +82,18 @@ func main () {
 	
 	log.Println(`.// initialized.`)
 
+	// be a daemon
 	ctx, done := context.WithCancel(context.Background())
 	daemon.OnSigint(done)
+	pidfile := daemon.PidFile(flagPidFile.Value)
+	if !pidfile.Empty() {
+		err := pidfile.Start()
+		if err != nil { log.Println("!!! could not write pid:", err) }
+		defer func () {
+			err := pidfile.Close()
+			if err != nil { log.Println("!!! could not delete pidfile:", err) }
+		} ()
+	}
 	
 	log.Printf("(i) listening on %s\n", httpServer.Addr)
 	if err := manager.Run(ctx); err != nil && !errors.Is(err, context.Canceled) {