text_formatter: detect tty based on fd

terminal_solaris.go

@@ -9,7 +9,13 @@ import (
 )
 
 // IsTerminal returns true if the given file descriptor is a terminal.
-func IsTerminal() bool {
-	_, err := unix.IoctlGetTermios(int(os.Stdout.Fd()), unix.TCGETA)
-	return err == nil
+func IsTerminal(f io.Writer) bool {
+	var termios Termios
+	switch v := f.(type) {
+	case *os.File:
+		_, err := unix.IoctlGetTermios(int(f.Fd()), unix.TCGETA)
+		return err == nil
+	default:
+		return false
+	}
 }