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+++ b/relpipe-data/examples-awk-changing-values.xml Tue May 28 21:18:20 2019 +0200
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+<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>Changing values with AWK</nadpis>
+ <perex>regular expression text replacement</perex>
+ <m:pořadí-příkladu>02300</m:pořadí-příkladu>
+
+ <text xmlns="http://www.w3.org/1999/xhtml">
+
+ <p>
+ Besides filtering, we can use an AWK transformation to modify attribute values.
+ This means simply rewriting the value of given variable in AWK and calling <code>record()</code> function at the end.
+ </p>
+
+ <p>For example we can move all volumes mounted under <code>/mnt/</code> to another directory using regular expressions:</p>
+
+ <m:pre jazyk="bash"><![CDATA[relpipe-in-fstab \
+ | relpipe-tr-awk \
+ --relation '.*' \
+ --for-each '{ mount_point = gensub("^/mnt/", "/mnt/old/", "g", mount_point); record(); }' \
+ | relpipe-out-tabular]]></m:pre>
+
+ <p>which will result in:</p>
+
+ <pre><![CDATA[fstab:
+ ╭─────────────────┬──────────────────────────────────────┬──────────────────────┬───────────────┬───────────────────────────────────────┬────────────────┬────────────────╮
+ │ scheme (string) │ device (string) │ mount_point (string) │ type (string) │ options (string) │ dump (integer) │ pass (integer) │
+ ├─────────────────┼──────────────────────────────────────┼──────────────────────┼───────────────┼───────────────────────────────────────┼────────────────┼────────────────┤
+ │ UUID │ 29758270-fd25-4a6c-a7bb-9a18302816af │ / │ ext4 │ relatime,user_xattr,errors=remount-ro │ 0 │ 1 │
+ │ │ /dev/sr0 │ /media/cdrom0 │ udf,iso9660 │ user,noauto │ 0 │ 0 │
+ │ │ /dev/sde │ /mnt/old/data │ ext4 │ relatime,user_xattr,errors=remount-ro │ 0 │ 2 │
+ │ UUID │ a2b5f230-a795-4f6f-a39b-9b57686c86d5 │ /home │ btrfs │ relatime │ 0 │ 2 │
+ │ │ /dev/mapper/sdf_crypt │ /mnt/old/private │ xfs │ relatime │ 0 │ 2 │
+ ╰─────────────────┴──────────────────────────────────────┴──────────────────────┴───────────────┴───────────────────────────────────────┴────────────────┴────────────────╯
+Record count: 5]]></pre>
+
+ <p>
+ We can modify multiple attributes in a single transformation
+ and we can also use other AWK functions like <code>toupper()</code>, <code>tolower()</code> etc.
+ </p>
+
+ </text>
+
+</stránka>