wall - write a message to all users
wall [-n] [-t timeout] [-g group] [message | file]
wall displays a message, or the contents of a file, or otherwise its standard input, on the terminals of all currently logged in users. The command will wrap lines that are longer than 79 characters. Short lines are whitespace padded to have 79 characters. The command will always put a carriage return and new line at the end of each line.
Only the superuser can write on the terminals of users who have chosen to deny messages or are using a program which automatically denies messages.
Reading from a file is refused when the invoker is not superuser and the program is set-user-ID or set-group-ID.
-t, --timeout timeout
-g, --group group
Some sessions, such as wdm(1x), that have in the beginning of utmp(5) ut_type data a ':' character will not get the message from wall. This is done to avoid write errors.
A wall command appeared in Version 7 AT&T UNIX.
For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.
The wall command is part of the util-linux package which can be downloaded from Linux Kernel Archive https://www.kernel.org/pub/linux/utils/util-linux/.