wall.8

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th WALL VIII 4/10/75
.sh NAME
wall  \*-  write to all users
.sh SYNOPSIS
.bd /etc/wall
.sh DESCRIPTION
.it 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 ...''.
It is used to warn all users,
typically prior to shutting down the system.
.s3
The sender should be super-user to override
any protections the users may have invoked.
.sh FILES
/dev/tty?
.sh "SEE ALSO"
mesg (I), write (I)
.sh DIAGNOSTICS
``Cannot send to ...'' when the open on
a user's tty file fails.
.sh BUGS