wall (Unix)

wall (an abbreviation of write to all) is a Unix command-line utility that displays the contents of a file or standard input to all logged-in users. It is typically used by root to send out shutting down message to all users just before poweroff.

Invocation

wall reads the message from standard input by default when the filename is omitted. This is done by piping the output of the echo command:

alice@sleipnir:~$ # `tty` to show the current terminal name
alice@sleipnir:~$ tty
/dev/pts/7
alice@sleipnir:~$ echo Remember to brush your teeth! | wall

The message may also be typed in much the same way cat is used; invoking wall by typing wall and pressing ↵ Enter followed by a message, pressing ↵ Enter and Ctrl+D:

alice@sleipnir:~$ wall
Remember to brush your teeth!
^D

Using a here-string:

alice@sleipnir:~$ wall <<< 'Remember to brush your teeth!'

Reading from a file is also supported:

alice@sleipnir:~$ cat .important_announcement
Remember to brush your teeth!
alice@sleipnir:~$ wall .important_announcement # same as `wall !$`

All the commands above should display the following output on terminals that users allow write access to (see mesg(1)):

Broadcast Message from alice@sleipnir
  (/dev/pts/7) at 16:15 ...

Remember to brush your teeth!

References

wall(1) – Version 7 Unix Programmer's Manual
wall(1) – Linux User Commands Manual
wall(1) – FreeBSD General Commands Manual
wall(1M) – Solaris 10 System Administration Commands Reference Manual

Unix command-line interface programs and shell builtins

File system	cat chmod chown chgrp cksum cmp cp dd du df file fsck fuser ln ls mkdir mount mv pax pwd rm rmdir split tee touch type umask

Processes	at bg chroot cron fg kill killall nice pgrep pkill ps pstree time top

User environment	clear env exit finger history logname mesg passwd su sudo uptime talk tput uname w wall who whoami write

Text processing	awk banner basename comm csplit cut diff dirname ed ex fmt fold head iconv join less more nl paste printf sed sort spell strings tail tr uniq vi wc xargs yes

Shell builtins	alias cd echo test unset wait

Networking	dig host ifconfig inetd netcat netstat nslookup ping rdate rlogin route ssh traceroute

Searching	find grep locate whatis whereis

Documentation	apropos help man

Miscellaneous	bc dc cal expr lp od sleep true and false

List of Unix commands

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