Implement ttyname() in case /dev/tty is not available

Close #1266
Close #447

src/tui/ttyname_unix.go

@@ -0,0 +1,31 @@
+// +build !windows
+
+package tui
+
+import (
+	"io/ioutil"
+	"syscall"
+)
+
+var devPrefixes = [...]string{"/dev/pts/", "/dev/"}
+
+func ttyname() string {
+	var stderr syscall.Stat_t
+	if syscall.Fstat(2, &stderr) != nil {
+		return ""
+	}
+
+	for _, prefix := range devPrefixes {
+		files, err := ioutil.ReadDir(prefix)
+		if err != nil {
+			continue
+		}
+
+		for _, file := range files {
+			if stat, ok := file.Sys().(*syscall.Stat_t); ok && stat.Rdev == stderr.Rdev {
+				return prefix + file.Name()
+			}
+		}
+	}
+	return ""
+}