clipmenu-spmenu/clipmenud

#!/bin/bash

cache_dir=/tmp/clipmenu.$USER/
mkdir -p -m0700 "$cache_dir"

declare -A last_data

while sleep "${CLIPMENUD_SLEEP:-0.5}"; do
    for selection in clipboard primary; do
        if type -p xsel >/dev/null 2>&1; then
            data=$(xsel --"$selection"; printf x)
            xsel --"$selection" | xsel -i --"$selection"
        else
            data=$(xclip -o -sel "$selection"; printf x)
            xclip -o -sel "$selection" | xclip -i -sel "$selection"
        fi

        # We add and remove the x so that trailing newlines are not stripped.
        # Otherwise, they would be stripped by the very nature of how POSIX
        # defines command substitution.
        data=${data%x}

        [[ $data == *[^[:blank:]]* ]] || continue

        [[ ${last_data[$selection]} == "$data" ]] && continue
        last_data[$selection]=$data

        md5=$(md5sum <<< "$data")
        md5=${md5%% *}

        printf '%s' "$data" > "$cache_dir/$(LC_ALL=C date +%F-%H-%M-%S)-$md5"
    done
done