Find duplicate lines in a file and count how many time each line was duplicated?

https://stackoverflow.com/questions/6712437/find-duplicate-lines-in-a-file-and-count-how-many-time-each-line-was-duplicated

Assuming there is one number per line:

sort  | uniq -c

You can use the more verbose --count flag too with the GNU version, e.g., on Linux:

sort  | uniq --count