"... mi koze ahhoz, hogy az explicit device-ba (>/dev/tty) iras nem futyul?"
Az, hogy nincs mögötte ilyen terminal. A /dev/tty nem az egész rendszerre vonatkozóan egyedi, hanem csak a processzre. Azaz két külön process által elért /dev/tty nem feltétlen jelenti ugyanazt a terminált. Ha a crondt futtató gépen szeretnél csipogást, akkor inkább például a /dev/tty1-et használd.
38.6 The Controlling Terminal:
"But just what is a controlling terminal? Just what it sounds like: the terminal from which the process was started."
"How does a process "lose" its controlling terminal? Easy. Some processes, such as system "daemons" (1.14) never had one - they were started by system scripts that weren't started from any terminal, or they disconnected themselves from their controlling terminals. But it's also possible that you started a process running in the background, logged out, and logged back later or on another terminal to find it still running without a controlling terminal."
"Running tty without a controlling terminal gives the message not a tty."