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

perl -lne '$h{$_}++; END{for $n (sort keys %h) {print "$n\t$h{$n}"}}' input.txt

Loop over each line with -n
Each $_ number increments hash %h
Once the END of input.txt has been reached,
sort {$a <=> $b} the hash numerically
Print the number $n and the frequency $h{$n}

Similar code which works on floating point:

perl -lne '$h{int($_)}++; END{for $n (sort {$a <=> $b} keys %h) {print "$n\t$h{$n}"}}' float.txt

float.txt

1.732
2.236
1.442
3.162
1.260
0.707

output:

0       1
1       3
2       1
3       1