termstatus: Don't print status if in background

internal/ui/termstatus/background.go

@@ -0,0 +1,9 @@
+// +build !linux
+
+package termstatus
+
+// IsProcessBackground reports whether the current process is running in the
+// background. Not implemented for this platform.
+func IsProcessBackground() bool {
+	return false
+}

internal/ui/termstatus/background_linux.go

@@ -0,0 +1,21 @@
+package termstatus
+
+import (
+	"syscall"
+	"unsafe"
+
+	"github.com/restic/restic/internal/debug"
+)
+
+// IsProcessBackground reports whether the current process is running in the background.
+func IsProcessBackground() bool {
+	var pid int
+	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(syscall.Stdin), syscall.TIOCGPGRP, uintptr(unsafe.Pointer(&pid)))
+
+	if err != 0 {
+		debug.Log("Can't check if we are in the background. Using default behaviour. Error: %s\n", err.Error())
+		return false
+	}
+
+	return pid != syscall.Getpgrp()
+}

internal/ui/termstatus/status.go

@@ -95,6 +95,10 @@ func (t *Terminal) run(ctx context.Context) {
 	for {
 		select {
 		case <-ctx.Done():
+			if IsProcessBackground() {
+				// ignore all messages, do nothing, we are in the background process group
+				continue
+			}
 			t.undoStatus(statusLines)
 
 			err := t.wr.Flush()
@@ -105,6 +109,10 @@ func (t *Terminal) run(ctx context.Context) {
 			return
 
 		case msg := <-t.msg:
+			if IsProcessBackground() {
+				// ignore all messages, do nothing, we are in the background process group
+				continue
+			}
 			t.undoStatus(statusLines)
 
 			var dst io.Writer
@@ -144,6 +152,10 @@ func (t *Terminal) run(ctx context.Context) {
 			}
 
 		case stat := <-t.status:
+			if IsProcessBackground() {
+				// ignore all messages, do nothing, we are in the background process group
+				continue
+			}
 			t.undoStatus(statusLines)
 
 			statusBuf.Reset()