handle errors in whiptail gauge with a msgbox

Question

I am trying to run a whiptail gauge where I am showing progress as multiple commands are run. I have some error checking, but since the commands are running in a subshell, I can't seem to display the error in a msgbox. Any help would be greatly appreciated! Below is a sample of what I have tried:

#!/usr/bin/env bash
{
   echo 0
   some_cmd1
   if [ $? -ne 0 ]; then
      whiptail --msgbox "error running cmd" 8 48
   fi
   echo 20
   some_cmd2
   if [ $? -ne 0 ]; then
      whiptail --msgbox "error running cmd" 8 48
   fi
   ...
   echo 100
} | whiptail --gauge "checking pre-reqs..." 8 48 0

I've also tried returning a status code, but I'm at a loss of how to utilize it if since it's being piped into whiptail

#!/usr/bin/env bash
{
   echo 0
   some_cmd1
   if [ $? -ne 0 ]; then
      echo "error running cmd"
      return 1
   fi
   echo 20
   some_cmd2
   if [ $? -ne 0 ]; then
      echo "error running cmd"
      return 1
   fi
   ...
   echo 100
} | whiptail --gauge "checking pre-reqs..." 8 48 0

Also, if I'm going about this wrong, please let me know as well!

Answer 1

Like this:

#!/usr/bin/env bash

myfunc() {
   echo 0

   sleep 1

   echo 20
   sleep 1
   if ! false; then
      whiptail --msgbox "error running cmd" 8 48 >&2
      return 1
   fi
   :
   echo 100
   sleep 1
}

myfunc | whiptail --gauge "checking pre-reqs..." 8 48 0