Tty (unix)

In computing, tty is a command in Unix and Unix-like operating systems to print the file name of the terminal connected to standard input.
tty stands for TeleTYpewriter.
Usage.
The codice_1 command is commonly used to check if the output medium is a terminal. The command prints the file name of the terminal connected to standard input. If no file is detected (in case, it's being run as part of a script or the command is being piped) "codice_2" is printed to stdout and the command exits with an exit status of 1. The command also can be run in silent mode (codice_3) where no output is produced, and the command exits with an appropriate exit status.