Retrieve / assign latest mtime

latest.bash

# Find the last modified file selected from a glob.
# Usage: latest <glob> <varname>
# Takes an optional glob and optional varname.
# glob defaults to '*'. If varname is set, assign to varname,
# else output to stdout.
function latest {
    if [[ $FUNCNAME == "${FUNCNAME[1]}" ]]; then
        unset -v x latest files
        printf -v "$@"
    elif (($# > 2)); then
        printf '%s\n' "Usage: $FUNCNAME <glob> <varname>" 'Error: Takes at most 2 arguments. Glob defaults to *'
        return 1
    else
        if ! shopt -q nullglob; then
            typeset -f +t "$FUNCNAME"
            trap 'shopt -u nullglob; trap - RETURN' RETURN
            shopt -s nullglob
        fi

        IFS= typeset -a 'files=(${1:-*})'
        typeset latest x

        for x in "${files[@]}"; do
            [[ -d $x || $x -ot $latest ]] || latest=$x
        done

        ${2:+"$FUNCNAME"} "${2:-printf}" -- %s "$latest"
    fi
}