Shell Programming and Scripting

a1
b2
a2
c2
d1
f3

 a1 1.2 0.5 0.06 0.7 0.9 1 0.023
a3  0.91 0.007 0.12 0.34 0.45 1 0.7 
a2  1.05 2.3 0.25 1 0.9 0.3 0.091
b1 1 5.4 0.3 9.2 0.3 0.2 0.1
b2 3 5 7 0.9 1 9 0 1
b3 0.001 1 2.3 4.6 8.9 10 0 1 0
c1 0.9 1 2.3 5.7 8.9 9 0 1
c2 1 2.4 5.7 0.13 1.9 2 5 8
c3 5.7 9 10 11 0.2 0.7 0.9
d1 9.0 5 8 4.5 9 0.99 1.3 1 0
d2 2 4.6 7 9 9 10 11 0 1 2.4 0.44
f1 7 8 4.5 6.8 9.21 0 1 8 4 9 10
f3 0 1 2.3 4.0 3.14 0 1 0.005

a1 1.2 0.5 0.06 0.7 0.9 1 0.023
b2 3 5 7 0.9 1 9 0 1
a2  1.05 2.3 0.25 1 0.9 0.3 0.091
c2 1 2.4 5.7 0.13 1.9 2 5 8
d1 9.0 5 8 4.5 9 0.99 1.3 1 0
f3 0 1 2.3 4.0 3.14 0 1 0.005

< datafile awk '
BEGIN { FS="\t"
        # get the very first key.
        getline key < "keyfile" }
{
        # If the data's ahead in order, read keys until you catch up
        # but don't read keys past EOF.
        while(key && (key < $1))
                getline key < "keyfile"

        if(key && (key == $1))
                print;
}'