UNIX for Advanced & Expert Users

{
print "tableA tableB tableC
1 1 3
2 3 2
3 2 1

tableD tableE tableF
4 4 6
5 6 5
6 3 4
" | nawk '

    # New Column headings 
    /table/ {
        # For each field (column heading)
        for (i=1; i<=NF; i++) {
           # Save the current column headings
           current[i]=$(i)
    
           # Save an array pointer...
           arrs[$(i)]=i
    
           # ...and an array index
           arrs_idx[$(i)]=1
        }
        # Move on
        getline
    }
    
    # Each non column heading record
    {
        # For each column heading (table name)...
        for (i=1; i<=NF; i++) {
            # Create a record in table_array, indexed by the table name and its current index (based on current headings)
            table_array[current[i] OFS arrs_idx[current[i]]++] = $(i)
        }
    }
    
    END {
        # For each table in the table array...
        for (i in arrs) {
            # Print its table name
            print ""
            print i
            print "========="

            # For each record in the array...
            for (j=1; j<=3; j++) {
                #  Print the element
                print table_array[i OFS j]
            }
        }
    }
    '
}

tableA
=========
1
2
3

tableB
=========
1
3
2

tableC
=========
3
2
1

tableD
=========
4
5
6

tableE
=========
4
6
3

tableF
=========
6
5
4