robustly select lines from file; can replace the head and tail shell commands and do even more

usage: get_line {--range|-r} {+n|-n|i|i..j|i,j[,...]} [-i FILE] [--rand] [-v] (1 <= i [<= j] <= N; N = nb. lines in FILE)

-v invert the selection of lines (like 'grep -v') --rand randomize selected lines before writing them out -i <filename> where to read lines from (default=stdin) -o <filename> where to write lines to (default=stdout) {-r|--range} {+n|-n|i|i..j|i,j[,...]}: line selection policy;

           (+n => top n lines;
            -n => last n lines;
            n => only line n;
            i..j => lines i to j;
            i,j[,...] => only lines i,j,...

{-help|--help} Display this list of options