Sort an array of pathnames of files by their basenames

sort in GNU coreutils allows custom field separator and key. You set / as field separator and sort based on second field to sort on the basename, instead of entire path.

printf "%s\n" "${filearray[@]}" | sort -t/ -k2 will produce

dir2/0003.pdf
dir1/0010.pdf
dir3/0040.pdf

Sorting with gawk expression (supported by bash's readarray):

Sample array of filenames containing whitespaces:

filearray=("dir1/name 0010.pdf" "dir2/name  0003.pdf" "dir3/name 0040.pdf")

---

readarray -t sortedfilearr < <(printf '%s\n' "${filearray[@]}" | awk -F'/' '
   BEGIN{PROCINFO["sorted_in"]="@val_num_asc"}
   { a[$0]=$NF }
   END{ for(i in a) print i}')

The output:

echo "${sortedfilearr[*]}"
dir2/name 0003.pdf dir1/name 0010.pdf dir3/name 0040.pdf

Accessing single item:

echo "${sortedfilearr[1]}"
dir1/name 0010.pdf

That assumes that no file path contains newline characters. Note that the numerical sorting of the values in @val_num_asc only applies to the leading numerical part of the key (none in this example) with fallback to lexical comparison (based on strcmp(), not the locale's sorting order) for ties.

oldIFS="$IFS"; IFS=$'\n'
if [[ -o noglob ]]; then
  setglob=1; set -o noglob
else
  setglob=0
fi

sorted=( $(printf '%s\n' "${filearray[@]}" |
            awk '{ print $NF, $0 }' FS='/' OFS='/' |
            sort | cut -d'/' -f2- ) )

IFS="$oldIFS"; unset oldIFS
(( setglob == 1 )) && set +o noglob
unset setglob

Sorting of file names with newlines in their names will cause issues at the sort step.

It generates a /-delimited list with awk that contains the basename in the first column and the complete path as the remaining columns:

0003.pdf/dir2/0003.pdf
0010.pdf/dir1/0010.pdf
0040.pdf/dir3/0040.pdf

This is what is sorted, and cut is used to remove the first /-delimited column. The result is turned into a new bash array.