Count the number of lines in a file without reading entire file into memory?

Question

I\'m processing huge data files (millions of lines each).

Before I start processing I\'d like to get a count of the number of lines in the file, so I can then indic

Answer 1

If the file is a CSV file, the length of the records should be pretty uniform if the content of the file is numeric. Wouldn't it make sense to just divide the size of the file by the length of the record or a mean of the first 100 records.