Quite often, I find myself thinking that it would be good to have a general solution that is as portable as possible, "if I ever need this on a weird or constraint machine".
I have been searching for a way to more or less efficiently sort a list of files in a directory in reverse order, using POSIX sh and tools only.
This should work with arbitrarily named files, including such with control code characters (e.g., newlines) in their name.
So the idea is to process a set of files in lexicographical reverse order. As you know, you cannot parse ls, due to the weird filenames. Since this is POSIX, we don't have arrays. So here is a solution that might work.
Glob expressions return a list of possible filenames in lexicographical order. So you could do something like
for file in /path/to/dir/*; do
[ -e "${file}" ] || continue
some_command "${file}"
done
If you want to reverse it, you can just do:
set -- /path/to/dir/*
i=$#
while [ "$i" -gt 0 ]; do
eval "file=\${${i}}"; i=$((i-1));
[ -e "${file}" ] || continue
some_command "$file"
done
Note: we have to use an evil eval for the evaluation of the positional variable.
Update: it is possible that positional variables are already in use. In this case you can do the following:
j=$#
set -- /path/to/dir/* "$@"
i=$(($#-$j))
while [ "$i" -gt 0 ]; do
eval "file=\${${i}}"; i=$((i-1));
[ -e "${file}" ] || continue
some_command "$file"
done
shift "$i"