--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/relpipe-data/examples-filesystem-xattr.xml Tue Feb 05 19:18:28 2019 +0100
@@ -0,0 +1,67 @@
+<stránka
+ xmlns="https://trac.frantovo.cz/xml-web-generator/wiki/xmlns/strana"
+ xmlns:m="https://trac.frantovo.cz/xml-web-generator/wiki/xmlns/makro">
+
+ <nadpis>Reading extended attributes using relpipe-in-filesystem</nadpis>
+ <perex>accessing xattr of given files e.g. xdg.origin.url</perex>
+ <m:pořadí-příkladu>01300</m:pořadí-příkladu>
+
+ <text xmlns="http://www.w3.org/1999/xhtml">
+
+
+ <p>
+ Extended attributes (xattr) are additional <em>key=value</em> pairs that can be attached to our files.
+ They are not stored inside the files, but on the filesystem.
+ Thus they are independent of particular file format (which might not support metadata)
+ and we can use them e.g. for tagging, cataloguing or adding some notes to our files.
+ Some tools like GNU Wget use extended attributes to store metadata like the original URL from which the file was downloaded.
+ </p>
+
+ <m:pre jazyk="bash"><![CDATA[wget --recursive --level=1 https://relational-pipes.globalcode.info/
+find -type f -printf '%P\0' \
+ | relpipe-in-filesystem --file path --file size --xattr xdg.origin.url \
+ | relpipe-out-tabular
+]]></m:pre>
+
+ <p>And now we know, where the files on our disk came from:</p>
+
+ <pre><![CDATA[filesystem:
+ ╭───────────────────────────┬────────────────┬────────────────────────────────────────────────────────────────────╮
+ │ path (string) │ size (integer) │ xdg.origin.url (string) │
+ ├───────────────────────────┼────────────────┼────────────────────────────────────────────────────────────────────┤
+ │ index.html │ 12159 │ https://relational-pipes.globalcode.info/v_0/ │
+ │ v_0/atom.xml │ 4613 │ https://relational-pipes.globalcode.info/v_0/atom.xml │
+ │ v_0/rss.xml │ 4926 │ https://relational-pipes.globalcode.info/v_0/rss.xml │
+ │ v_0/js/skript.js │ 2126 │ https://relational-pipes.globalcode.info/v_0/js/skript.js │
+ │ v_0/css/styl.css │ 2988 │ https://relational-pipes.globalcode.info/v_0/css/styl.css │
+ │ v_0/css/relpipe.css │ 1095 │ https://relational-pipes.globalcode.info/v_0/css/relpipe.css │
+ │ v_0/css/syntaxe.css │ 3584 │ https://relational-pipes.globalcode.info/v_0/css/syntaxe.css │
+ │ v_0/index.xhtml │ 12159 │ https://relational-pipes.globalcode.info/v_0/index.xhtml │
+ │ v_0/grafika/logo.png │ 3298 │ https://relational-pipes.globalcode.info/v_0/grafika/logo.png │
+ │ v_0/principles.xhtml │ 17171 │ https://relational-pipes.globalcode.info/v_0/principles.xhtml │
+ │ v_0/roadmap.xhtml │ 11097 │ https://relational-pipes.globalcode.info/v_0/roadmap.xhtml │
+ │ v_0/faq.xhtml │ 11080 │ https://relational-pipes.globalcode.info/v_0/faq.xhtml │
+ │ v_0/specification.xhtml │ 12983 │ https://relational-pipes.globalcode.info/v_0/specification.xhtml │
+ │ v_0/implementation.xhtml │ 10810 │ https://relational-pipes.globalcode.info/v_0/implementation.xhtml │
+ │ v_0/examples.xhtml │ 76958 │ https://relational-pipes.globalcode.info/v_0/examples.xhtml │
+ │ v_0/license.xhtml │ 65580 │ https://relational-pipes.globalcode.info/v_0/license.xhtml │
+ │ v_0/screenshots.xhtml │ 5708 │ https://relational-pipes.globalcode.info/v_0/screenshots.xhtml │
+ │ v_0/download.xhtml │ 5204 │ https://relational-pipes.globalcode.info/v_0/download.xhtml │
+ │ v_0/contact.xhtml │ 4940 │ https://relational-pipes.globalcode.info/v_0/contact.xhtml │
+ │ v_0/classic-example.xhtml │ 9539 │ https://relational-pipes.globalcode.info/v_0/classic-example.xhtml │
+ ╰───────────────────────────┴────────────────┴────────────────────────────────────────────────────────────────────╯
+Record count: 20]]></pre>
+
+ <p>
+ If we like the BeOS/Haiku style, we can create empty files with some attributes attached and use our filesystem as a simple database
+ and query it using relational tools.
+ It will lack indexing, but for basic scenarios like <em>address book</em> it will be fast enough
+ and we can feel a bit of BeOS/Haiku atmosphere in our contemporary GNU/Linux systems.
+ But be careful with that because some editors delete and recreate files while saving them, which destroys the xattrs.
+ Tools like <code>rsync</code> or <code>tar</code> with <code>--xattrs</code> option will backup our attributes securely.
+ </p>
+
+
+ </text>
+
+</stránka>