#!/bin/bash

# Load both data files into memory
< trydata1 mapfile data1
< trydata2 mapfile data2
for f1 in ${data1[*]};
do
    lines=$(( $lines + 1 ))
    kee2=$(echo $f1 | cut -d, -f4)
    for val2 in ${data2[*]};
    do
        if [[ $val2 =~ ^$kee2 ]]; then
            repl=${val2##*,}
            sed -i "$lines s/\b$kee2/$repl/g" trydata1
        fi
    done
done
cat trydata1

# Using this data set with no column issues...
# ----------------------
# xyz,122,913,opq,876
# rst,956,921,xyz,012
# 456,890,903,rst,467
# 000,5xyz1,000,xyz,000
# 4567,5rst1,opq,xyz,000
# rst,5opq1,rst,02opq,000
# 000,5xyz1,xyz,opq,000

# real    0m0.028s
# user    0m0.008s
# sys    0m0.009s

# On a machine running @ 2GHz
# If my math is right...
# 0.028 seconds to process 7 lines
# time to process 30,000 lines ~ 2 minutes