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Vernor Vinge's novel A Deepness in the Sky describes a spacefaring trading civilization thousands of years in the future that still uses the Unix epoch.
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wall(1) [bsd man page]

WALL(1) 						      General Commands Manual							   WALL(1)

NAME
wall - write to all users SYNOPSIS
wall DESCRIPTION
Wall reads its standard input until an end-of-file. It then sends this message, preceded by `Broadcast Message ...', to all logged in users. The sender should be super-user to override any protections the users may have invoked. FILES
/dev/tty? /var/run/utmp SEE ALSO
mesg(1), write(1) DIAGNOSTICS
`Cannot send to ...' when the open on a user's tty file fails. 4th Berkeley Distribution November 27, 1996 WALL(1)

Check Out this Related Man Page

wall(1M)						  System Administration Commands						  wall(1M)

NAME
wall - write to all users SYNOPSIS
/usr/sbin/wall [-a] [-g grpname] [filename] DESCRIPTION
wall reads its standard input until an end-of-file. It then sends this message to all currently logged-in users preceded by: Broadcast Message from ... If filename is given, then the message is read in from that file. Normally, pseudo-terminals that do not correspond to rlogin sessions are ignored. Thus, when using a window system, the message appears only on the console window. However, -a will send the message even to such pseudo-terminals. It is used to warn all users, typically prior to shutting down the system. The sender must be superuser to override any protections the users may have invoked See mesg(1). wall runs setgid() to the group ID tty, in order to have write permissions on other user's terminals. See setuid(2). wall will detect non-printable characters before sending them to the user's terminal. Control characters will appear as a " ^ " followed by the appropriate ASCII character; characters with the high-order bit set will appear in "meta" notation. For example, `03' is dis- played as `^C' and `372' as `M-z'. OPTIONS
The following options are supported: -a Broadcast message to the console and pseudo-terminals. -g grpname Broadcast to the users in a specified group only, per the group database (see group(4)). ENVIRONMENT VARIABLES
If the LC_* variables (LC_CTYPE, LC_TIME, LC_COLLATE, LC_NUMERIC, and LC_MONETARY) are not set in the environment, the operational behav- ior of wall for each corresponding locale category is determined by the value of the LANG environment variable. See environ(5). If LC_ALL is set, its contents are used to override both the LANG and the other LC_* variables. If none of the above variables are set in the envi- ronment, the "C" (U.S. style) locale determines how wall behaves. FILES
/dev/tty* ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------------------------------------+ |ATTRIBUTE TYPE ATTRIBUTE VALUE | |Availability SUNWcsu | +-----------------------------------------------------------+ SEE ALSO
mesg(1), write(1), setuid(2), attributes(5), environ(5) NOTES
wall displays ``Cannot send to ...'' when the open on a user's tty file fails. SunOS 5.11 13 Jul 1994 wall(1M)

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