wall

Broadcast a message (UNIX)

Syntax:

wall [-a|-l|-n node] [-fFTv] [file]

Options:

-a

Write to all users on all nodes. Counteracts -l. (Default)

-f

Ignore the qnx_net_alive() node list; attempt to write to all nodes between 1 and the highest node number licensed.

-F

Don't fork multiple copies. (To speed up operation, wall defaults to forking num_alive_nodes/10 agent processes, with a maximum of 20. Each agent uses a timer and several virtual circuits.)

-l

("el") Local. Write to users on the local node only. Counteracts -a.

-n node[-node]

Write to all users on the specified node, or range of nodes. A range without a second node (e.g. n-) will be taken to mean "nodes n to the highest node ID the system is licensed for." Only a single -n option may be specified.

-T

Test mode. All actions are performed except for the actual writing to the destination ttys. Diagnostic messages are written indicating the actions that would have been taken.

-v

Verbose. Indicate persons/ttys to which messages are being delivered, as they are delivered.

-x node[-node][,...]

Exclude this node from the set of nodes being written to. Node ranges may also be specified. Multiple nodes or ranges may be specified, separated by commas, e.g. wall -x1,2,200-300 A range without a second node (e.g. n-) will be taken to mean "nodes n to the highest node ID the system is licensed for."

file

The pathname of a file containing a message to be sent (default is standard input).

Description:

You use the wall utility to broadcast a message to all users logged in on all nodes of the network, or optionally to users only on a specific node. By default, wall reads the message to be submitted from standard input. Once wall has been invoked, enter the message, then press Ctrl-D to submit the message.

The wall utility now writes to all users on the network by default. Versions previous to QNX4.23 had required the -a option to do this. A -l option is available to restrict writing to users on the local node only.

If you use the wall utility while you are root (superuser), you should include your real name in the text of the message so recipients will know who is responsible for the message.

Where multiple -a, -l, or -n options appear, the option appearing last on the command line will take effect. Multiple -n node options may not be specified.

There is a ten second timeout on attempting to write to any one tty. If the ten seconds elapses before the entire message has been submitted, wall will abandon the effort and move on to the next tty. Usually a partial message will appear on the tty that was being written to when this occurs.

Examples:

If user root issues the following:

# wall
Warning!  Rebooting file server in three minutes for OS upgrade
If this is inconvenient come see me (glen) now!
^D

It will broadcast a message like this to all users on the network:

Broadcast message from root (//34/dev/con3) at Thu Oct 24 15:49:01
Warning!  Rebooting file server in three minutes for OS upgrade
If this is inconvenient come see me (glen) now!
EOT

Non-root users can also use wall, but they are not guaranteed to have write permission for the target ttys. If the user issuing wall does not have write permission for the tty, that tty will be skipped and wall will continue delivering the message to the remaining ttys.

Caveats:

If nameloc managers are being run on nodes which should not be providing name services (see nameloc for guidelines), the network alive list may show many nodes as being down which are in fact up. This can result in only a fraction of the users on the system receiving the message from wall. If you have users on your network who regularly break the nameloc rules, it is recommended that you always use the -f option to wall.

See also:

write