Send SIGHUP to parent process when woke up

main.go

@@ -5,22 +5,26 @@ import (
 	"flag"
 	"io"
 	"log"
+	"math"
 	"math/rand"
 	"os"
 	"os/exec"
+	"os/signal"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 
 	"github.com/faiface/beep"
 	"github.com/faiface/beep/effects"
-	"github.com/faiface/beep/speaker"
 	"github.com/faiface/beep/flac"
 	"github.com/faiface/beep/mp3"
+	"github.com/faiface/beep/speaker"
 )
 
 const (
 	SampleRate = beep.SampleRate(48000)
+	MaxRunTime = 1 * time.Hour
 )
 
 func xPrintIdle() (idle uint64) {
@@ -72,7 +76,7 @@ func loadFile(path string) (s beep.Streamer, err error) {
 func main() {
 	flag.Parse()
 
-	if len(flag.Args()) < 2 {
+	if len(flag.Args()) < 1 {
 		log.Println("missing required argument:  input file name")
 		return
 	}
@@ -116,19 +120,36 @@ func main() {
 
 	launched := time.Now()
 	idle := xPrintIdle()
+	ntick := 0
+
+	// Prepare graceful shutdown
+	maxRun := time.After(MaxRunTime)
+	interrupt := make(chan os.Signal, 1)
+	signal.Notify(interrupt, os.Interrupt, syscall.SIGTERM)
+
 loop:
 	for {
-		select{
+		select {
-		case t := <-ticker.C:
+		case <-maxRun:
-			if volume.Volume < 0 {
-				volume.Volume += 0.007
-			}
-			if t.Sub(launched) > 1 * time.Hour {
 			break loop
-			}
+		case <-ticker.C:
+			ntick += 1
+			volume.Volume = -2 - math.Log(5/float64(ntick))/3
+
 			if xPrintIdle() < idle {
 				break loop
 			}
+		case <-interrupt:
+			break loop
+		}
+	}
+
+	// Tell parent process that it can launch the wake up procedure
+	if time.Now().Sub(launched) < MaxRunTime {
+		if proc, err := os.FindProcess(os.Getppid()); err != nil {
+			log.Println(err)
+		} else if err := proc.Signal(syscall.SIGHUP); err != nil {
+			log.Println(err)
 		}
 	}