+//usage:#define tty_trivial_usage
+//usage: ""
+//usage:#define tty_full_usage "\n\n"
+//usage: "Print file name of stdin's terminal"
+//usage: IF_INCLUDE_SUSv2( "\n"
+//usage: "\n -s Print nothing, only return exit status"
+//usage: )
+//usage:
+//usage:#define tty_example_usage
+//usage: "$ tty\n"
+//usage: "/dev/tty2\n"
+