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

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