Read and Modify the key value in XML using Bash/Shell script

Question

I need to read (store in variable) and then change the online_hostname key value in XML using bash/shell script.

<?xml version="1.0" encoding="UTF-8" ?>
<bzinfo>
    <myidentity online_hostname="testdevice-air_2022_01_25" 
                bzlogin="[email protected]" />
</bzinfo>

I am able to read the value but not able to change it.

cat test.xml | grep '<myidentity ' | sed -E 's/.*online_hostname="?([^ "]*)"? .*/\1/'

Obligatory parsing XML with regex

jordanm
– jordanm

2022-04-18 14:28:25 +00:00
Commented Apr 18, 2022 at 14:28 — jordanm
– jordanm, Commented Apr 18, 2022 at 14:28

Reino · Accepted Answer · 2022-04-24 00:24:33Z

2

Please DO NOT use sed to parse/edit XML! Use an XML-parser instead.

With xidel:

$ xidel -s input.xml -e '
  x:replace-nodes(//@online_hostname,function($x){attribute {name($x)} {"newhost"}})
' --output-format=xml --output-node-indent

With xmlstarlet:

$ xmlstarlet ed -u '//@online_hostname' -v 'newhost' input.xml

answered Apr 24, 2022 at 0:24

Reino

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Comments

Pepe N O · Accepted Answer · 2022-04-19 21:29:42Z

1

Storing in the environment variable

MYVAR="newhost"

It could be solved like this

sed -rie 's@online_hostname="(.*?) (.*)"@online_hostname="'$MYVAR'" \2@' test.xml

the first group of regular expression matches lazy to " in other words, first appearance of ". The second group (.*) meaning anything, is preserved in \2, using @ as separator -i as in-place of and r as extended regular expressions.

edited Apr 19, 2022 at 21:29

answered Apr 18, 2022 at 16:21

Pepe N O

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3 Comments

Karthikeyan M Over a year ago

I am getting the below error when trying sed. "sed: 1: "test.xml": undefined label 'est.xml' ". Also I need the value of online_hostname in a variable. Thanks.

Karthikeyan M Over a year ago

Also <myidentity online_hostname="michael-g’s-macbook-air_2022_04_18" bzlogin="[email protected]" /> is a one liner. This command removes the bzlogin="[email protected] part. Thanks.

Karthikeyan M Over a year ago

sed: 1: "s@online_hostname="(.*? ...": RE error: repetition-operator operand invalid - I tried the new command, got this error. I am on trying on macOS. Is that specific I am missing? Thanks

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