generating frequency table from file
Solution 1:
You mean you want a count of how many times an item appears in the input file? First sort it (using -n if the input is always numbers as in your example) then count the unique results.
sort -n input.txt | uniq -c
Solution 2:
Another option:
awk '{n[$1]++} END {for (i in n) print i,n[i]}' input.txt | sort -n > output.txt