Stuck at finding the most recent file from a list of directories

Question

I want to find a list of directories, then search for a given file inside them, then choose the most recent one.

This is what I try:

find /Temp -type d -name Ast 2>/dev/null | while read Dir; do find $Dir -type f -name Pagination.json 2>/dev/null -exec ls -lt {} +; done

This indeed brings me the intended files, but it sorts them ascendingly.

This is the result of that command:

-rw-r--r-- 1 root root 46667 Sep 12 18:10 /Temp/ProjectOne/Site/Ast/BaseComponents/Pagination.json
-rw-r--r-- 1 root root 46667 Sep 13 09:31 /Temp/ProjectTwo/Site/Ast/BaseComponents/Pagination.json

In this case, I need the second item. What should I do?

Answer 1

The way I'd approach this is using the shell's own file-finding abilities to find all candidates, then keep the newest one:

#!/bin/bash
enable ** as recursive glob, don't fail when null matches are found, and
also look into things starting with .
shopt -s globstar nullglob dotglob
newestmod=0
for candidate in /Ast//Pagination.json ; do
    # check file type:
    [[ -f ${candidate} ]] || continue
    [[ -L ${candidate} ]] && continue
    # Get modification time in seconds since epoch without fractional
    # part. Assumes GNU stat or compatible.
    thisdate=$(stat -c '%Y' -- "${candidate}")
# if older than the newest found, skip 
[[ ${thisdate} -lt ${newestmod} ]] && continue

newestmod=${thisdate}
newestfile="${candidate}"

done
if (( newestmod )); then
  printf 'Newest file: "%s"\n' "${newestfile}"
fi

or such.

In zsh, that whole thing becomes a bit less complicated and supports subsecond precision in timestamps:

#!/usr/bin/zsh
#get the list of regular (.) files, ordered by modification date
allcandidates=(/Ast//Pagination.json(ND.om))
if (( $#allcondidates )) print -r Newest file: $allcandidates[1]

Or just:

print -r Newest file: **/Ast/**/Pagination.json(D.om[1])

Beware that while **/ in zsh and bash5.0+ don't follow symlinks when recursively traversing the directory tree, the Ast/ part would traverse symlinks. If that were a concern, in zsh, you could work around it with:

set -o extendedglob
print -r Newest file: ./**/Pagination.json~^*/Ast/*(D.om[1])

Where ./**/Pagination.json finds all the files without traversing symlinks but ~pattern removes the paths that match the pattern, here the ones that don't (^) contain /Ast/.

Answer 2

It changes a little depending upon what you precisely mean by "most recent", but wherever the GNU implementation of find is available, and if we know there are not file paths containing newline characters, I would use something like:

find /tmp -type f -printf "%T@ %p\n" | sort -rn

(adjust /tmp -type f to find the files you actually care about, it will probably be something like find /Temp -path '*/Ast/*' -type f -name 'Pagination.json'). The interesting part is %T@ which prints file's last modification time in seconds since epoch, that's quite easy to sort by.