WALL(1M)            RISC/os Reference Manual             WALL(1M)



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; char-
     acters with the high-order bit set will appear in meta nota-
     tion. For example, `\003' is displayed as `^C' and `\372' as
     `M-z'.

     wall forks a process to write its message for each line in
     /etc/utmp which has a ut_type field ut_type USER_PROCESS. If
     wall can't fork a process, if it fails to write the message
     to any given session in 60 seconds, or if any of the forked
     processes fail to terminate in 60 seconds, then the program
     will exit with an alarm signal.  When the Bourne shell sees
     a child process exit with an alarm signal it prints "Alarm
     call".  Thus the message "Alarm call" or "Alarm clock" (from
     csh) means that at least one user on the system may not have
     recieved the message.

INTERNATIONAL FUNCTIONALITY
     wall can send characters from supplementary codesets.

     wall uses the locale of the sender to determine printablil-
     ity.

FILES
     /dev/tty*

SEE ALSO
     mesg(1), write(1).




                        Printed 11/19/92                   Page 1

WALL(1M)            RISC/os Reference Manual             WALL(1M)



NOTES
     ``Cannot send to ...'' when the open on a user's tty file
     fails.




















































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