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
Reading from a file is refused when the invoker is not
superuser and the program is set-user-ID or set-group-ID.
Suppress the banner.
-t, --timeout timeout
Abandon the write attempt to the terminals after
timeout seconds. This timeout must be a positive integer. The
default value is 300 seconds, which is a legacy from the time when people ran
terminals over modem lines.
-g, --group group
Limit printing message to members of group defined as a
group argument. The argument can be group name or GID.
Display version information and exit.
Display help text and exit.
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.