gistfile1.sh

#!/bin/sh

file=/etc/postgresql/9.1/main/postgresql.conf
current=`egrep "^[ 	]*bytea_output[ 	]*=" $file | tr -d "' 	" | cut -f1 -d\# | tr = ' ' | cut -f2 -d' '`

case "$current" in
     '' ) echo "bytea_output = 'escape'" >> $file ;;
     escape) ;;  # Do nothing, the existing value is correct.
     hex) echo "Incompatible setting: $current"; exit 1;;
     *) echo "wtf.... unknown value $current"; exit 2;;
esac