Question

Having two files written in the form of associative array (key=value) like:

file A:

banana=yellow
kiwi=green
tomato=red

file B:

banana=dislike
tomato=like
pear=like

I would like to know the best approach (in term of speed) to compare their keys:

A against B:

kiwi=green

B against A

pear=like

bidirectional

kiwi=green
pear=like

I would prefer not to use loops as those files can be huge.

Answer 1

B against A

awk -F'=' 'NR==FNR{a[$1]=$0;next}!($1 in a)' A B

A against B

awk -F'=' 'NR==FNR{a[$1]=$0;next}!($1 in a)' B A

bidirectional

awk -F'=' '{a[$1]++;v[$1]=$0}END{for(i in a)if(a[i]==1)print v[i]}' A B

all not tested, let me know if it doesn’t work.