#! /usr/bin/ksh

OLD_IFS="$IFS"
IFS=","

while read field1 field2 field3 field4 ; do
    echo "field1=$field1 field2=$field2 field3=$field3 field4=$field4"
done < file

IFS="$OLD_IFS"

[root@MYAUSLV00100118 tmp]# cat ./foo.ksh
#! /bin/bash

while read line; do
    field1=`echo "${line}" | sed 's/^\([^,]*\),.*$/\1/'`
    field2=`echo "${line}" | sed 's/^[^,]*,\([^,]*\),.*$/\1/'`
    field3=`echo "${line}" | sed 's/^[^,]*,[^,]*,\(\"[^\"]*\"\),.*$/\1/'`
    field4=`echo "${line}" | sed 's/^[^,]*,[^,]*,\"[^\"]*\",\([^,]*\).*$/\1/'`
    echo "field1=${field1}"
    echo "field2=${field2}"
    echo "field3=${field3}"
    echo "field4=${field4}"
done < foo.csv

exit 0
[root@MYAUSLV00100118 tmp]# cat ./foo.csv
"FSNAME_01102006B_input.csv",10,"First Name, Last Name"," CUST"
[root@MYAUSLV00100118 tmp]# ./foo.ksh
field1="FSNAME_01102006B_input.csv"
field2=10
field3="First Name, Last Name"
field4=" CUST"