текстовый редактор (text editor)
Стандартный ввод (Stdin)
The standard input consists of a series of commands and input
text, as described in the EXTENDED DESCRIPTION section. The
implementation may limit each line of standard input to a length
of {LINE_MAX}.
If the standard input is not a terminal device, it shall be as if
the -s option had been specified.
If a read from the standard input returns an error, or if the
editor detects an end-of-file condition from the standard input,
it shall be equivalent to a SIGHUP asynchronous event.
