wall(ADM)

wall -- write to all users

Syntax

/etc/wall [ -g group ] [ file ]

Description

The wall command reads a message from file or the standard input until an end-of-file is received. wall sends this message to all users currently logged in. The message is preceded by a header detailing who generated the message, the system name, and the time.

wall is used to warn all users, for example, prior to shutting down the system.

If a group is specified using the -g option, wall sends a message only to that group.

The sender should be root to override any protections that users may have set on their terminal lines using mesg(C).

Diagnostics

file??: the message file could not be opened
Cannot send to ...: the user's terminal line could not be opened for writing
Only one group allowed: only one group can be selected
Unknown group group: group is not in /etc/group

Limitations

wall will fail if /etc/utmp does not exist, cannot be opened for reading, or is too large.

Files

/etc/group: groups defined on this system
/etc/utmp: information about users logged onto the system
/dev/tty[01][0-9]: device files for console multiscreens
/dev/tty[12][a-hA-H]: device files for serial ports
/dev/ttyp: device files for pseudo ttys

Standards conformance

wall is conformant with:

AT&T SVID Issue 2;
X/Open Portability Guide, Issue 3, 1990: note that the X/Open CAE Specification, Commands and Utilities, Issue 4, 1992 marks this command as withdrawn.