map='p.map'

function init() {
cat <<EOF > $map
apple a
boy b
cat c
dog d
elephant e
EOF
}

function put() {
    k=$1; v=$2;
    del $k
    echo $v $k >> $map
 }

function get() {
    k=$1
    for v in $(cat $map | grep "$k$"); do
        echo $v
        break
    done
 }

function del() {
    k=$1
    temp=$(mktemp)
    mv $map $temp
    cat $temp | grep -v "$k$" > $map
}

function dump() {
    echo "-- Dump begin --"
    cat $map
    echo "-- Dump complete --"
}

init
get c
put c cow
get c
dump