Removing content of a column based on number of occurences - awk

Question

I have a file (; seperated) with data like this
111111121;000-000.1;000-000.2
111111211;000-000.1;000-000.2
111112111;000-000.1;000-000.2
111121111;000-000.1;000-000.2
111211111;000-000.1;000-000.2
112111111;000-000.1;000-000.2
121111112;000-000.2;020-000.8
121111121;000-000.2;020-000.8
121111211;000-000.2;020-000.8
121113111;000-000.3;000-200.2
211111121;000-000.1;000-000.2
I would like to remove any $3 that has less than 3 occurences, so the outcome would be like
111111121;000-000.1;000-000.2
111111211;000-000.1;000-000.2
111112111;000-000.1;000-000.2
111121111;000-000.1;000-000.2
111211111;000-000.1;000-000.2
112111111;000-000.1;000-000.2
121111112;000-000.2;020-000.8
121111121;000-000.2;020-000.8
121111211;000-000.2;020-000.8
121113111;000-000.3
211111121;000-000.1;000-000.2
That is, only $3 got deleted, as it had only a single occurence
Sadly I am not really sure if (thus how) this could be done relatively easily (as doing the =COUNT.IF matching, and manuel delete in Excel feels quite embarrassing)

Answer 1

$ awk -F';' 'NR==FNR{cnt[$3]++;next} cnt[$3]<3{sub(/;[^;]+$/,"")} 1' file file
111111121;000-000.1;000-000.2
111111211;000-000.1;000-000.2
111112111;000-000.1;000-000.2
111121111;000-000.1;000-000.2
111211111;000-000.1;000-000.2
112111111;000-000.1;000-000.2
121111112;000-000.2;020-000.8
121111121;000-000.2;020-000.8
121111211;000-000.2;020-000.8
121113111;000-000.3
211111121;000-000.1;000-000.2
or if you prefer:
$ awk -F';' 'NR==FNR{cnt[$3]++;next} {print (cnt[$3]<3 ? $1 FS $2 : $0)}' file file

Answer 2

this awk one-liner can help, it processes the file twice:
awk -F';' 'NR==FNR{a[$3]++;next}a[$3]<3{NF--}7' file file

Answer 3

Though that awk solutions are the best in terms of performance, your goal could be also achieved with something like this:
while IFS=" " read a b;do
if [[ "$a" -lt "3" ]];then
sed -i "s/$b//" b.txt
fi
done <<<"$(cut -d";" -f3 b.txt |sort |uniq -c)"
Operation is based on the output of cut which counts occurrences.
$cut -d";" -f3 b.txt |sort |uniq -c
7 000-000.2
1 000-200.2
3 020-000.8
Above works for editing source file in place, so keep a back up for testing.

Answer 4

You can feed the file twice to awk. On the first run you gather a statistic that you use in the second run:
script.awk
FNR == NR { stats[ $3 ]++
next
}
{ if( stats[$3] < 3) print $1 $2
else print
}
Run it like this: awk -F\; -f script.awk yourfile yourfile .
The condition FNR == NR is true during processing of the first filename given to awk. The next statement skips the second block.
Thus the second block is only used for processing the second filename given to awk (which is here the same as the first filename).