обрабатывать сообщения (process messages)
Асинхронные события (Asynchronous events)
When mailx is in Send Mode and standard input is not a terminal,
it shall take the standard action for all signals.
In Receive Mode, or in Send Mode when standard input is a
terminal, if a SIGINT signal is received:
1. If in command mode, the current command, if there is one,
shall be aborted, and a command-mode prompt shall be written.
2. If in input mode:
a. If ignore is set, mailx shall write "@\n", discard the
current input line, and continue processing, bypassing
the message-abort mechanism described in item 2b.
b. If the interrupt was received while sending mail, either
when in Receive Mode or in Send Mode, a message shall be
written, and another subsequent interrupt, with no other
intervening characters typed, shall be required to abort
the mail message. If in Receive Mode and another
interrupt is received, a command-mode prompt shall be
written. If in Send Mode and another interrupt is
received, mailx shall terminate with a non-zero status.
In both cases listed in item b, if the message is not
empty:
i. If save is enabled and the file named by DEAD can be
created, the message shall be written to the file
named by DEAD. If the file exists, the message
shall be written to replace the contents of the
file.
ii. If save is not enabled, or the file named by DEAD
cannot be created, the message shall not be saved.
The mailx utility shall take the standard action for all other
signals.
