--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/relpipe-data/examples-grep-fstab.xml Tue Feb 05 19:18:28 2019 +0100
@@ -0,0 +1,44 @@
+<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>Filtering /etc/fstab using relpipe-tr-grep</nadpis>
+ <perex>list only records with desired filesystem types</perex>
+ <m:pořadí-příkladu>00900</m:pořadí-příkladu>
+
+ <text xmlns="http://www.w3.org/1999/xhtml">
+
+ <p>
+ If we are interested only in certain records in some relation, we can filter it using <code>relpipe-tr-grep</code>.
+ If we want to list e.g. only Btrfs and XFS file systems from our <code>fstab</code> (see above), we will run:
+ </p>
+
+
+ <m:pre jazyk="bash"><![CDATA[relpipe-in-fstab | relpipe-tr-grep 'fstab' 'type' 'btrfs|xfs' | relpipe-out-tabular]]></m:pre>
+
+ <p>and we will get following filtered result:</p>
+ <pre><![CDATA[fstab:
+ ╭─────────────────┬──────────────────────────────────────┬──────────────────────┬───────────────┬──────────────────┬────────────────┬────────────────╮
+ │ scheme (string) │ device (string) │ mount_point (string) │ type (string) │ options (string) │ dump (integer) │ pass (integer) │
+ ├─────────────────┼──────────────────────────────────────┼──────────────────────┼───────────────┼──────────────────┼────────────────┼────────────────┤
+ │ UUID │ a2b5f230-a795-4f6f-a39b-9b57686c86d5 │ /home │ btrfs │ relatime │ 0 │ 2 │
+ │ │ /dev/mapper/sdf_crypt │ /mnt/private │ xfs │ relatime │ 0 │ 2 │
+ ╰─────────────────┴──────────────────────────────────────┴──────────────────────┴───────────────┴──────────────────┴────────────────┴────────────────╯
+Record count: 2]]></pre>
+
+ <p>
+ Command arguments are similar to <code>relpipe-tr-sed</code>.
+ Everything is a regular expression.
+ Only relations matching the regex will be filtered, others will flow through the pipeline unmodified.
+ If the attribute regex matches more attribute names, filtering will be done with logical OR
+ i.e. the record is included if at least one of that attributes matches the search regex.
+ </p>
+
+ <p>
+ If we need exact match of the whole attribute, we have to use something like <code>'^btrfs|xfs$'</code>,
+ otherwise mere substring-match is enough to include the record.
+ </p>
+
+ </text>
+
+</stránka>