NAME

wall − write to all users

SYNOPSIS

/usr/sbin/wall

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 . . .

It is used to warn all users, typically prior to shutting down the system. 

The sender must be super-user to override any protections the users may have invoked [see mesg(1)]. 

wall runs setgid() [see setuid(2)] to the group ID tty, in order to have write permissions on other user’s terminals. 

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, ‘\003’ is displayed as ‘^C’ and ‘\372’ as ‘M−z’. 

INTERNATIONAL FUNCTIONS

wall can send characters from supplementary codesets. 

wall uses the locale of the sender to determine printablility. 

FILES

/dev/tty∗

SEE ALSO

mesg(1), write(1)

NOTES

“Cannot send to . . .” when the open on a user’s tty file fails.