capturefd3numfd.sh

#!/bin/sh

# Nothing up my sleeve...
unset ANSWER

# dupe stdout (fd 1) to fd 4 (using redirection)
# change the shell's idea of what stdout is to be fd 4 (exec)
exec 4>&1

# set-up a command substitution
# the command is a subshell expression, with redirection applied
#   the redirection dupes stdout again, on to fd 3
# the subshell itself invokves dialog(1)
#   we apply redirection to this to put dialog's output back on the terminal
#   and we tell dialog to send its results to the fd 3 we opened earlier
ANSWER=$( ( dialog --output-fd 3 --inputbox 'Speak Friend and enter' 0 0  > /dev/fd/4 ) 3>&1 )

# Ta-da!
echo ANSWER=\<$ANSWER\>