[TUHS] Re: Likely a one-liner in Unix

Hi James, Given sort(1) gained -u for efficiency, I've often wondered why, in those constrained times, it didn't have a ‘-m n’ to output only the n ‘minimums’, e.g. ‘sed ${n}q’. With ‘-m 5’, this would let sort track the current fifth entry and discard input which was bigger, so avoiding both storing many unwanted lines and finding the current line's location within them. I think the POSIX way of getting the atime would be ‘LC_CTIME=C ls -lu’ and then parsing the two possible date formats. So non-POSIX find is simpler. Also, GNU find shows me the sub-second part but ls doesn't. Neither does GNU ‘stat -c '%X %n'’. - I'd switch the atime format to seconds since epoch for easier formatting given it's discarded. - When atimes tie, sort's -r will give file Z before A so I'd add some -k's so A comes first. - I'd move the head to before the cut so cut processes fewer lines... - But on so few lines, I'd just use sed to do both in one. find "$@" -type f -printf '%A@ %p\n' | sort -k1,1nr -k2 | sed 's/^[^ ]* //; 5q' Remaining issues... If tied entries bridge the top-five border then this isn't shown. Is the real requirement to show files with the five most recent distinct atimes? awk '{t += !s[$0]; s[$0] = 1; print} t == 5 {exit}' Though this might give many lines. Instead, an ellipsis could show a tie bridged the cut-off. awk 't {if ($0 == l) print "..."; exit} NR == 5 {l = $0; t = 1} 1' Paths can contain linefeeds and some versions allow handling NULs to be tediously employed. find "$@" -type f -printf '%A@ %p\0' | sort -z -k1,1nr -k2 | sed -z 's/[^ ]* //; 5q' | tr \\0 \\n David Wheeler has a nice article he maintains on unusual characters in filenames: how to cope, and what other systems do, e.g. Plan 9. Fixing Unix/Linux/POSIX filenames: control characters (such as newline), leading dashes, and other problems David A. Wheeler, 2023-08-22 (originally 2009-03-24) https://dwheeler.com/essays/fixing-unix-linux-filenames.html As he writes, Linux already returns EINVAL for some paths on some filesystem types. A mount option which had a syscall return an error on meeting an insensible path would be useful. It avoids any attempt at escapement and its greater risk of implementation errors. I could always re-mount some old volume without the option to list the directory and fix up its entries. The second-best day to plant a tree is today. -- Cheers, Ralph.