sankaku-downloader.sh

#!/bin/bash

# Downloads images from Sankaku Channel, by tag list.
# It accepts a space-separated list of tags as first argument (see example)
# and outputs downloaded images to a directory named after the tags.
# Notice that forbidden characters will be replaced by the question character (�).

tagCount=$(tr -dc ' ' <<< " $1" | awk '{ print length; }')

if [[ -z "$1" ]] || grep -qE '^-h|--help$' <<< "$1" || ((tagCount > 4)); then
    echo 'Please provide a list of up to 4 tags as the first argument.'
    echo 'example:'
    echo "    sankaku-downloader.sh 'hjl brown_hair -rating:e'"
    exit 0
fi

encodeURIComponent() {
    perl -pe 's/([^a-zA-Z0-9_.!~*()'\''-])/sprintf("%%%02X", ord($1))/ge';
}

tags="$(encodeURIComponent <<< "$1")"
dirName="$(head -n1 <<< "$1" | sed -r 's#[\/:*?"<>|]#�#g')"
chan='https://chan.sankakucomplex.com'

getResultPage() {
    curl -s "$chan/post/index.content?tags=$baseUrl$tags&page=$1"
}

pageNumber=0
nextPage() {
    let pageNumber++
    pageContent="$(getResultPage $pageNumber)"
    if (($?)); then return 1; fi
    grep -q '/post/show/' <<< "$pageContent"
}

getUrls() {
    grep '/post/show/' | sed -r 's/^.*?href="//g;s/".*$//g'
}

downloadPost() {
    html="$(curl -s "$1")"
    if (($?)); then echo -n ' X'; return 1; fi
    re='cs\.sankakucomplex\.com/data/[a-f0-9]'
    sed="s#^.*($re)#https://\\1#;s/\".*\$//"
    url="$(grep -E "$re" <<< "$html" | head -n1 | sed -r "$sed")"
    fileName="$(sed 's#^.*/##;s/\?.*$//' <<< "$url")"
    curl -s "$url" > "$dirName/$fileName"
    if (($?)); then echo -n ' X'; return 1; fi
    echo -n ' ✓'
}

anyPageYet=false
while nextPage; do
    anyPageYet=true
    mkdir -p "$dirName"
    if [[ ! -d "$dirName" ]]; then
        echo 'Cannot create a directory to store downloaded files here!'
        exit 1
    fi
    echo -n "Downloading page $pageNumber..."
    for post in $(getUrls <<< "$pageContent"); do
        downloadPost "$chan$post"
    done
    echo
done

if ! $anyPageYet; then
    echo "No results were found for \"$1\"."
fi