Displaying messages to tty using whiptail through monit

Question

I would like to display a whiptail message on the login screen that is triggered by monit, but I am without luck.

I understand it might be something to do with interactive/non-interactive shell. Here is the script that gets triggered by monit.

#!/bin/bash
/usr/bin/whiptail --infobox 'Hello World.' 7 25 >/dev/tty1

Is there a trick, or should I avoid using whiptail?

Answer 1

The "trick" is that whiptail (like dialog) writes its messages by default to the standard error, because conventional program use the standard output for screen updates.

You can redirect the standard error by putting a 2 next to the > mark:

#!/bin/bash
/usr/bin/whiptail --infobox 'Hello World.' 7 25 2>/dev/tty1

Further reading:

• whiptail - display dialog boxes from shell scripts
• How to use whiptail to write interactive shell scripts
• dialog - display dialog boxes from shell scripts

Answer 2

I just tried the following and was able to send output from my desktop to /dev/tty2 using whiptail so I think what you're doing would seem feasible. Couple of things that I noticed.

1. permissions

I needed to be root in order to send anything to /dev/tty2. I'm assuming you're running this as a monit user who would most likely not have permissions to send data to and tty device.

2. --infobox

The --infobox switch didn't appear to work in my current shell but I was able to send an --infobox to /dev/tty2. YMMV. --msgbox worked in both cases.