Shell Programming and Scripting

#!/bin/sh

while read line
do
  lookup=`echo "$line" | awk -vFS=',' '{print $1}'`
  field=`echo "$line" | awk -vFS=',' '{print $2}' | sed 's/^ //'`
  match=`grep "\<$lookup\>" file_b`
  if [ "$?" -eq "0" ]; then
    echo "$match" | while read record
    do
      echo "$record $field"
    done
  fi
done < file_a

BEGIN {
   FS=","
   while(getline<xref) arr[$1]=$2
   FS=" "
}
$3 in arr {
   print $0, arr[$3] 
}

#!/bin/sh

while read line
do
  lookup=`echo "$line" | awk -vFS=',' '{print $1}'`
  field=`echo "$line" | awk -vFS=',' '{print $2}' | sed 's/^ //'`
  match=`grep "\<$lookup\>" ${2}`
  if [ "$?" -eq "0" ]; then
    echo "$match" | while read record
    do
      echo "$record $field"
    done
  fi
done < ${1}