Line Counter

In short A line counter reports total lines, non-empty lines, duplicates and the longest line — four numbers that answer different questions. Total lines is what a text editor's status bar shows and what a log file's size is usually described in. Non-empty lines is what you want when checking a list, because trailing blank lines at the end of a paste are invisible and are counted by almost everything else. The duplicate count is the one that finds real problems: a list of 500 email addresses that reports 480 unique lines has twenty repeats in it, and that is worth knowing before you import it. Longest line matters more than it sounds, because fixed-width contexts break on it — a CSV column that overruns a database field, a code comment that exceeds a line-length rule, an email that wraps badly. One detail worth knowing: whether a file ends with a final newline changes the count by one in some tools and not others, which is why two programs can disagree about a file neither of them has changed.