wall (Unix)
Appearance
Developer(s) | AT&T Bell Laboratories |
---|---|
Initial release | May 1975 |
Operating system | Unix and Unix-like |
Type | Command |
wall (an abbreviation of write to all) is a Unix command-line utility that displays the contents of a computer 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
[edit]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!
See also
[edit]References
[edit]- Version 7 Unix Programmer's Manual –
- Linux User Commands Manual –
- FreeBSD General Commands Manual –
- Solaris 11.4 System Administration Commands Reference Manual –