Moved moved unix-related parts into terminal

internal/terminal/terminal_check_bsd.go

@@ -0,0 +1,13 @@
+// +build darwin dragonfly freebsd netbsd openbsd
+
+package terminal
+
+import "golang.org/x/sys/unix"
+
+const ioctlReadTermios = unix.TIOCGETA
+
+func IsTerminal(fd int) bool {
+	_, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
+	return err == nil
+}
+

internal/terminal/terminal_check_unix.go

@@ -0,0 +1,13 @@
+// +build linux aix
+
+package terminal
+
+import "golang.org/x/sys/unix"
+
+const ioctlReadTermios = unix.TCGETS
+
+func IsTerminal(fd int) bool {
+	_, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
+	return err == nil
+}
+