#!/bin/bash
for (( i=0; i<=960; i=$((i+20)) )) ; do
    for link in $(wget "http://yume.booru.org/index.php?page=post&s=list&tags=all&pid=$i" -O - "$@" \
    | egrep -o 'thumbnail_[a-zA-Z0-9]*.(jpg|png|gif|jpeg)' | sed 's/thumbnail_//g')
    do
        wget -nc http://img.booru.org/yume//images/1/$link
    done
done