How to print the count of value stored in an array using awk?

Question

I have this sample file -

$cat f
a a1
a a2
a a3
b b1
b b2
b b3
b b4
c c1
c c2
c c3

And to print the record side by side for a common column I used below -

$awk '{a[$1]=a[$1]OFS$2} END {for (k in a) print k ,a[k]}' f
a  a1 a2 a3
b  b1 b2 b3 b4
c  c1 c2 c3

How can I achieve below output in a single command, where last column is the count of record for a common column.

a  a1 a2 a3 3 
b  b1 b2 b3 b4 4 
c  c1 c2 c3 3

we can combine two command to achive this -

$awk '{a[$1]=a[$1]OFS$2} END {for (k in a) print k ,a[k]}' f|awk '{print $0, NF-1}'
a  a1 a2 a3 3
b  b1 b2 b3 b4 4
c  c1 c2 c3 3

Answer 1

One way is to use the return value of gsub - it returns number of substitutions made

$ awk '{a[$1]=a[$1]OFS$2}
       END {for (k in a) print k a[k], gsub(OFS, OFS, a[k])}' ip.txt 
a a1 a2 a3 3
b b1 b2 b3 b4 4
c c1 c2 c3 3

Note: I've also removed , between k a[k] - otherwise there'll be two spaces between 1st and 2nd columns