generating frequency table from file

Question

Given an input file containing one single number per line, how could I get a count of how many times an item occurred in that file?

cat input.txt
1
2
1
3
1
0
         


        

Answer 1

At least some of that can be done with

sort output.txt | uniq -c

But the order number count is reversed. This will fix that problem.

sort test.dat | uniq -c | awk '{print $2, $1}'