lib/atexit: factor from cmd so it can be used by backend/cache #1946

lib/atexit/atexit.go

@@ -0,0 +1,46 @@
+// Package atexit provides handling for functions you want called when
+// the program exits unexpectedly due to a signal.
+//
+// You should also make sure you call Run in the normal exit path.
+package atexit
+
+import (
+	"os"
+	"os/signal"
+	"sync"
+
+	"github.com/ncw/rclone/fs"
+)
+
+var (
+	fns          []func()
+	exitOnce     sync.Once
+	registerOnce sync.Once
+)
+
+// Register a function to be called on exit
+func Register(fn func()) {
+	fns = append(fns, fn)
+	// Run AtExit handlers on SIGINT or SIGTERM so everything gets
+	// tidied up properly
+	registerOnce.Do(func() {
+		go func() {
+			ch := make(chan os.Signal, 1)
+			signal.Notify(ch, os.Interrupt) // syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT
+			sig := <-ch
+			fs.Infof(nil, "Signal received: %s", sig)
+			Run()
+			fs.Infof(nil, "Exiting...")
+			os.Exit(0)
+		}()
+	})
+}
+
+// Run all the at exit functions if they haven't been run already
+func Run() {
+	exitOnce.Do(func() {
+		for _, fn := range fns {
+			fn()
+		}
+	})
+}