Function show_lines 

pub fn show_lines(
    text: &str,
    first: usize,
    limit: usize,
    max_bytes: usize,
) -> String

text’s lines from line first (counted from 1) as Read shows them: as they are, at most limit lines and about max_bytes bytes, and a last line saying how many lines were left out and the offset to read on from, or that first is past the end. Lines longer than a width are cut, marked […], and counted in a note: 2000 characters, or less when that lets the asked lines fit max_bytes, as in a file of long lines, but never below 100 characters.