How to find the time of the last access of any file under a directory in Linux.

Here is a one-liner to find the time of the last access of any file under a directory in Linux:

date -d @`find PATH_TO_DIR -type f -exec stat -c %X '{}' \; | \
  perl -ne 'use List::Util qw[min max]; BEGIN {$max=0;} chomp; $max = max($max,$_); END { print $max ."\n";}'`

Here's a bash script to do this on each file or directory underneath a specified directory:

#!/bin/bash
# use like:
#   least_used_nodes.bash [PATH_TO_DIR]
#
# If PATH_TO_DIR is omitted, the current directory is used.
#
# leaf nodes with spaces in them are not supported

dir="."
if [ "$#" -ne 0 ] ; then
    dir=$1
fi

declare -a access_times
for n in `\ls -1 $dir | egrep -v '^\.{1,2}\$'`  ; do
    echo "Analyzing $n"
    d=`find $dir/$n -type f -exec stat -c %X '{}' \; |\
      perl -ne 'use List::Util qw[min max]; BEGIN {$max=0;} chomp; $max = max($max,$_); END { print $max ."\n";}'`
    #echo $d
    access_times[$d]="${access_times[$d]} $n"
done
echo ""
echo ""
#echo ${access_times[@]}

echo "Printing access times youngest to oldest"
for d in `echo ${!access_times[@]} | sed -r 's/\\s+/\\n/g;' | sort -r` ; do
    #echo $d
    list=${access_times[$d]}
    for n in $list ; do
        echo `date -d @$d +"%Y.%m.%d %kh%Mm"` $n
    done
done