345 lines
10 KiB
Org Mode
345 lines
10 KiB
Org Mode
#+TITLE: RSS Generation
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#+SUBTITLE: How to generate RSS feed via command line
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#+AUTHOR: Yann Esposito
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#+EMAIL: yann@esposito.host
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#+DATE: [2019-09-30 Mon]
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#+KEYWORDS: programming, web
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#+DESCRIPTION: How I generate RSS feed via command line
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#+OPTIONS: auto-id:t
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#+begin_notes
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TL;DR: To generate an RSS file you need to provide many metadatas.
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Those metadata are not part of all HTML files.
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So generating RSS from a tree of HTML file is not straightforward.
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Here is the script I use.
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#+end_notes
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* RSS Problem
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:PROPERTIES:
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:CUSTOM_ID: rss-problem
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:END:
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RSS feed is meant to declare updates and new articles for a website.
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Each RSS entry must therefore have a date, an unique id, a title, maybe
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some categories, etc...
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For most blog platform or even static website generator, those meta infos
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are clearly put in the sources or in some DB.
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I use =org-mode= for generating my website, and the =ox-rss= is quite slow
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when generating an RSS with the full content of each item.
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Mainly, the way to achieve full content of my articles inside an RSS with
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=ox-rss= is by first creating a very big org file containing all the
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articles, and then transforming it in RSS. And this is very slow (many minutes).
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So a simpler idea inspired by lb[fn:lb] is to generate the RSS directly
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from the generated HTML files.
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The only difficulty is to find the metadata inside those HTML.
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Unfortunately there is no real standard for all those metas.
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Has there is no standard place to have all those meta informations inside
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an HTML file in order to use the HTML as source you'll need to "parse" the
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HTML file.
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For that purpose I use =html-xml-utils=[fn:hu].
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I wrote a simple zsh script; it starts with lot of variables to fill:
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#+begin_src bash
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# Directory
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webdir="_site" # directory containing your website html files
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postsdir="$webdir/posts" # directory containing the articles
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rssfile="$webdir/rss.xml" # the RSS file to generate
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# maximal number of articles to put in the RSS file
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maxarticles=10
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# RSS Metas
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rsstitle="her.esy.fun"
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rssurl="https://her.esy.fun/rss.xml"
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websiteurl="https://her.esy.fun"
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rssdescription="her.esy.fun articles, mostly random personal thoughts"
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rsslang="en"
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rssauthor="yann@esposito.host (Yann Esposito)"
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rssimgtitle="yogsototh"
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rssimgurl="https://her.esy.fun/img/FlatAvatar.png"
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#+end_src
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Then I set the accessor to extract the information I want from HTML files.
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It is quite unfortunate that there is no really strong convention for where
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to put article dates, article author email.
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There are metas for title and keywords thought.
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#+begin_src bash
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# HTML Accessors (similar to CSS accessors)
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dateaccessor='.article-date'
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contentaccessor='#content'
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# title and keyword shouldn't be changed
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titleaccessor='title'
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keywordsaccessor='meta[name=keywords]::attr(content)'
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#+end_src
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A few helper functions:
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#+begin_src bash
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formatdate() {
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# format the date for RSS
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local d=$1
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LC_TIME=en_US date --date $d +'%a, %d %b %Y %H:%M:%S %z'
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}
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finddate(){ < $1 hxselect -c $dateaccessor }
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findtitle(){ < $1 hxselect -c $titleaccessor }
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getcontent(){ < $1 hxselect $contentaccessor }
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findkeywords(){ < $1 hxselect -c $keywordsaccessor | sed 's/,//g' }
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mkcategories(){
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for keyword in $*; do
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printf "\\n<category>%s</category>" $keyword
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done
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}
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#+end_src
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The =mkcategories= will be used to add an RSS category for each keyword.
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And finally the real loop doing the work:
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#+begin_src bash
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tmpdir=$(mktemp -d) # create a temporary work dir
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typeset -a dates # an array to save dates of all articles
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dates=( )
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# for each HTML file we generate the XML for the item in a file
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# named ${d}-$(basename $fic).rss that naming convention will be useful to
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# sort article by date
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for fic in $postsdir/**/*.html; do
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blogfile="$(echo "$fic"|sed 's#^'$postsdir'/##')"
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printf "%-30s" $blogfile
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xfic="$tmpdir/$fic.xml"
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mkdir -p $(dirname $xfic)
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hxclean $fic > $xfic # create a cleaner HTML file to help hxselect work
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d=$(finddate $xfic)
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echo -n " [$d]"
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rssdate=$(formatdate $d)
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title=$(findtitle $xfic)
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keywords=( $(findkeywords $xfic) )
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printf ": %-55s" "$title ($keywords)"
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# up until here, we extracted the informations we need for the item
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categories=$(mkcategories $keywords)
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{ printf "\\n<item>"
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printf "\\n<title>%s</title>" "$title"
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printf "\\n<guid>%s</guid>" "${websiteurl}/${blogfile}"
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printf "\\n<pubDate>%s</pubDate>%s" "$rssdate"
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printf "%s" "$categories"
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printf "\\n<description><![CDATA[\\n%s\\n]]></description>" "$(getcontent "$xfic")"
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printf "\\n</item>\\n\\n"
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} >> "$tmpdir/${d}-$(basename $fic).rss"
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# we append the date to the list of dates
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dates=( $d $dates )
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echo " [${fg[green]}OK${reset_color}]"
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done
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# Now we publish the items in reverse newer articles first
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echo "Publishing"
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for fic in $(ls $tmpdir/*.rss | sort -r | head -n $maxarticles ); do
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echo "${fic:t}"
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cat $fic >> $tmpdir/rss
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done
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# we get the latest publish date
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rssmaxdate=$(formatdate $(for d in $dates; do echo $d; done | sort -r | head -n 1))
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# we put the current date for the latest build date
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rssbuilddate=$(formatdate $(date))
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# we generate the RSS file
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{
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# Write the preamble of the RSS file
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cat <<END
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<?xml version="1.0" encoding="utf-8"?>
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<rss version="2.0"
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xmlns:content="http://purl.org/rss/1.0/modules/content/"
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xmlns:wfw="http://wellformedweb.org/CommentAPI/"
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xmlns:dc="http://purl.org/dc/elements/1.1/"
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xmlns:atom="http://www.w3.org/2005/Atom"
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xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
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xmlns:slash="http://purl.org/rss/1.0/modules/slash/"
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xmlns:georss="http://www.georss.org/georss"
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xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"
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xmlns:media="http://search.yahoo.com/mrss/"><channel>
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<title>${rsstitle}</title>
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<atom:link href="${rssurl}" rel="self" type="application/rss+xml" />
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<link>${websiteurl}</link>
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<description><![CDATA[${rssdescription}]]></description>
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<language>${rsslang}</language>
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<pubDate>${rssmaxdate}</pubDate>
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<lastBuildDate>$rssbuilddate</lastBuildDate>
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<generator>mkrss.sh</generator>
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<webMaster>${rssauthor}</webMaster>
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<image>
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<url>${rssimgurl}</url>
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<title>${rssimgtitle}</title>
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<link>${websiteurl}</link>
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</image>
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END
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# write all items
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cat $tmpdir/rss
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# close the RSS file
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cat <<END
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</channel>
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</rss>
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END
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} > "$rssfile"
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# cleanup temporary directory
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rm -rf $tmpdir
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echo "RSS Generated"
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#+end_src
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** Full script
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:PROPERTIES:
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:CUSTOM_ID: full-script
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:END:
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Here is the full script I use:
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#+begin_src bash
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#!/usr/bin/env nix-shell
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#!nix-shell -i zsh
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# Directory
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webdir="_site"
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postsdir="$webdir/posts"
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rssfile="$webdir/rss.xml"
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# maximal number of articles to put in the RSS file
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maxarticles=10
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# RSS Metas
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rsstitle="her.esy.fun"
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rssurl="https://her.esy.fun/rss.xml"
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websiteurl="https://her.esy.fun"
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rssdescription="her.esy.fun articles, mostly random personal thoughts"
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rsslang="en"
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rssauthor="yann@esposito.host (Yann Esposito)"
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rssimgtitle="yogsototh"
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rssimgurl="https://her.esy.fun/img/FlatAvatar.png"
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# HTML Accessors (similar to CSS accessors)
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dateaccessor='.article-date'
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contentaccessor='#content'
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# title and keyword shouldn't be changed
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titleaccessor='title'
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keywordsaccessor='meta[name=keywords]::attr(content)'
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formatdate() {
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# format the date for RSS
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local d=$1
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LC_TIME=en_US date --date $d +'%a, %d %b %Y %H:%M:%S %z'
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}
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finddate(){ < $1 hxselect -c $dateaccessor }
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findtitle(){ < $1 hxselect -c $titleaccessor }
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getcontent(){ < $1 hxselect $contentaccessor }
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findkeywords(){ < $1 hxselect -c $keywordsaccessor | sed 's/,//g' }
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mkcategories(){
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for keyword in $*; do
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printf "\\n<category>%s</category>" $keyword
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done
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}
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autoload -U colors && colors
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tmpdir=$(mktemp -d)
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typeset -a dates
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dates=( )
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for fic in $postsdir/**/*.html; do
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blogfile="$(echo "$fic"|sed 's#^'$postsdir'/##')"
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printf "%-30s" $blogfile
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xfic="$tmpdir/$fic.xml"
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mkdir -p $(dirname $xfic)
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hxclean $fic > $xfic
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d=$(finddate $xfic)
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echo -n " [$d]"
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rssdate=$(formatdate $d)
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title=$(findtitle $xfic)
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keywords=( $(findkeywords $xfic) )
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printf ": %-55s" "$title ($keywords)"
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categories=$(mkcategories $keywords)
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{ printf "\\n<item>"
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printf "\\n<title>%s</title>" "$title"
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printf "\\n<guid>%s</guid>" "${websiteurl}/${blogfile}"
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printf "\\n<pubDate>%s</pubDate>%s" "$rssdate"
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printf "%s" "$categories"
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printf "\\n<description><![CDATA[\\n%s\\n]]></description>" "$(getcontent "$xfic")"
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printf "\\n</item>\\n\\n"
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} >> "$tmpdir/${d}-$(basename $fic).rss"
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dates=( $d $dates )
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echo " [${fg[green]}OK${reset_color}]"
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done
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echo "Publishing"
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for fic in $(ls $tmpdir/*.rss | sort -r | head -n $maxarticles ); do
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echo "${fic:t}"
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cat $fic >> $tmpdir/rss
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done
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rssmaxdate=$(formatdate $(for d in $dates; do echo $d; done | sort -r | head -n 1))
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rssbuilddate=$(formatdate $(date))
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{
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cat <<END
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<?xml version="1.0" encoding="utf-8"?>
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<rss version="2.0"
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xmlns:content="http://purl.org/rss/1.0/modules/content/"
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xmlns:wfw="http://wellformedweb.org/CommentAPI/"
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xmlns:dc="http://purl.org/dc/elements/1.1/"
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xmlns:atom="http://www.w3.org/2005/Atom"
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xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
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xmlns:slash="http://purl.org/rss/1.0/modules/slash/"
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xmlns:georss="http://www.georss.org/georss"
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xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"
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xmlns:media="http://search.yahoo.com/mrss/"><channel>
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<title>${rsstitle}</title>
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<atom:link href="${rssurl}" rel="self" type="application/rss+xml" />
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<link>${websiteurl}</link>
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<description><![CDATA[${rssdescription}]]></description>
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<language>${rsslang}</language>
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<pubDate>${rssmaxdate}</pubDate>
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<lastBuildDate>$rssbuilddate</lastBuildDate>
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<generator>mkrss.sh</generator>
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<webMaster>${rssauthor}</webMaster>
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<image>
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<url>${rssimgurl}</url>
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<title>${rssimgtitle}</title>
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<link>${websiteurl}</link>
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</image>
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END
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cat $tmpdir/rss
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cat <<END
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</channel>
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</rss>
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END
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} > "$rssfile"
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rm -rf $tmpdir
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echo "RSS Generated"
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#+end_src
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The =nix-shell= bang pattern is a neat trick to have all the dependencies I
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need when running my script, I could have added zsh, but my main concern
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was about =html-xml-utils=.
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Along my script I have a =shell.nix= file containing:
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#+begin_src nix
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{ pkgs ? import (fetchTarball https://github.com/NixOS/nixpkgs/archive/19.09-beta.tar.gz) {} }:
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pkgs.mkShell {
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buildInputs = [ pkgs.html-xml-utils ];
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}
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#+end_src
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If you are not already using nix[fn:nix] you should really take a look.
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That =shell.nix= will work on Linux and MacOS.
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[fn:lb] https://github.com/LukeSmithxyz/lb
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[fn:hu] https://www.w3.org/Tools/HTML-XML-utils/
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[fn:nix] https://nixos.org/nix
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