HPR4417: Newest matching file

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Overview Several years ago I wrote a Bash script to perform a task I need to perform almost every day - find the newest file in a series of files. At this point I was running a camera on a Raspberry Pi which was attached to a window and viewed my back garden. I was taking a picture every 15 minutes, giving them names containing the date and time, and storing them in a directory. It was useful to be able to display the latest picture. Since then, I have found that searching for newest files useful in many contexts: Find the image generated by my random recipe chooser, put in the clipboard and send it to the Telegram channel for my family. Generate a weather report from wttr.in and send it to Matrix. Find the screenshot I just made and put it in the clipboard. Of course, I could just use the same name when writing these various files, rather than accumulating several, but I often want to look back through such collections. If I am concerned about such files accumulating in an unwanted way I write cron scripts which run every day and delete the oldest ones. Original script The first iteration of the script was actually written as a Bash function which was loaded at login time. The function is called newest_matching_file and it takes two arguments: A file glob expression to match the file I am looking for. An optional directory to look for the file. If this is omitted, then the current directory will be used. The first version of this function was a bit awkward since it used a for loop to scan the directory, using the glob pattern to find the file. Since Bash glob pattern searches will return the search pattern when they fail, it was necessary to use the nullglob (see references) option to prevent this, turning it on before the search and off afterwards. This technique was replaced later with a pipeline using the find command. Improved Bash script The version using find is what I will explain here. function newest_matching_file { local glob_pattern=${1-} local dir=${2:-$PWD} # Argument number check if [[ $# -eq 0 || $# -gt 2 ]]; then echo 'Usage: newest_matching_file GLOB_PATTERN [DIR]' >&2 return 1 fi # Check the target directory if [[ ! -d $dir ]]; then echo "Unable to find directory $dir" >&2 return 1 fi local newest_file # shellcheck disable=SC2016 newest_file=$(find "$dir" -maxdepth 1 -name "$glob_pattern" \ -type f -printf "%T@ %p\n" | sort | sed -ne '${s/.\+ //;p}') # Use printf instead of echo in case the file name begins with '-' [[ -n $newest_file ]] && printf '%s\n' "$newest_file" return 0 } The function is in the file newest_matching_file_1.sh , and it's loaded ("sourced", or declared) like this: . newest_matching_file_1.sh The '.' is a short-hand version of the command source . I actually have two versions of this function, with the second one using a regular expression, which the find command is able to search with, but I prefer this one. Explanation The first two lines beginning with local define variables local to the function holding the arguments. The first, glob_pattern is expected to contain some