#!/bin/ksh
#< Testing configuration file parsing with ksh
# Can parse out variable = value assignments and then
# uses eval to set shell variables as appropriate - therefore
# you must know which variables are being set so you can reference
# them later. When reading configuration files, you'd normally know
# what needs to be set and what doesn't - and you can check that these
# "pre-known" variables are set and throw errors otherwise....

CONFIG_FILE="./sh_config.conf"
i=0

# Initialise array to lines of file
while read line; do
  initial_array[${i}]="${line}"
  (( i = i + 1 ))
done < ${CONFIG_FILE}

# Set IFS to \n for processing file arrays
oldIFS=${IFS}
IFS='
'

# Comment removal ###########################################
i=0
for line in ${initial_array[@]}; do
   # Test for lines starting with '#'
   echo "${line}" | grep "^#.*$" >/dev/null 2>&1
   if [ "$?" -ne "0" ]; then
      # get rid of any inline comments
      no_comment=`echo "${line}" | sed "s/^\([^#]*\)#.*$/\1/"`
      processed_array[${i}]=${no_comment}    
      (( i = i + 1 ))
   fi
done

# Assignment validation #####################################
for line in ${processed_array[@]}; do
   echo "${line}" | egrep "^[^=]+=[^=]+$" >/dev/null 2>&1
   if [ "$?" -eq "0" ]; then
      # valid syntax
      # remove leading spaces
      first_pass=`echo ${line} |\
          sed "s/^[ 	]*\([^=]*\).*$/\1/"`
      # remove trailing spaces
      second_pass=`echo ${line} |\
          sed -e "s/[ 	]*$//" -e "s/^[^=]*=\([^=]*\)/\1/"`
      # put parts back together
      line="${first_pass}=${second_pass}"
      # remove the assignment operator
      variable=`echo ${line} |\
           sed -e "s/[ 	]*=/=/" -e "s/^\([^=]*\)=[^=]*$/\1/"`
      echo "${variable}" | grep '[[:space:]]' >/dev/null 2>&1
      if [ "$?" -eq "0" ]; then
         echo -en "WARNING: \"${variable}\" contains spaces as " >&2
         echo -en "a variable name - assignment ignored\n" >&2    
         continue
      fi
      value=`echo ${line} |\
          sed -e "s/=[ 	]*/=/" -e "s/^[^=]*=\([^=]*\)/\1/"` 
      export IFS
      eval ${variable}="\"${value}\""
   else
      :
      # invalid syntax
   fi
done

IFS=${oldIFS}

# Now we can cycle through our pre-known variables here checking them
# and acting on them as appropriate.
echo ${backup_dir}
echo ${some_var}

exit 0