Use xmlstarlet to remove an entire element that matches an attribute value?

Question

My question is similar to sed - Delete XML node containing certain element - Unix & Linux Stack Exchange. Trying to implement the suggestions there has kept me busy all day, but I haven't managed to get anything to work, so I am posting a question.

Within a bash script, I need to remove an entire <folder> element when the id attribute matches a given value. I'm actually using user-groups to do part of this. Say a user is not in the group folder_a; then the entire <folder> element with attribute id=".Folder_A" should be deleted from config.xml. (I also delete the folder from disk.)

My bash script looks like this:

#!/bin/bash

grouplist=$(groups $theuser);
for foldername in '.Folder_A' '.Folder_B'; do
  grpnm="${foldername,,}"|sed -e 's/^.//'
  if ! [[ $grouplist =~ ${grpnm} ]]; then
    perl -0777 -pe "s|(<folder.*?</folder>)|$1=~ /id=\"$foldername\"/?"":$1|gse" config.xml > config.xml
    rm -fr "$foldername"
  else
    echo "permitting access to ${foldername}"
  fi
done

The perl command is not working. It is just one of many variants I have tried. I also tried sed. I would prefer to use xmlstarlet, but I had even more trouble with it.

Edit - I just found this answer: https://unix.stackexchange.com/a/339089/393289 It helped me come up with this:

xml ed -d '//configuration/folder[contains(@id,".Folder_A")]' config.xml

I feel like I am closer now. (I tried to upvote that answer but I don't have enough rep yet.) However, I can't translate the attribute name into a bash variable yet due to the quote marks or something else.

BTW, how do I make that perform an in-place edit (similar to the sed -i command) once I get it working?

Here's an example config.xml file:

    <?xml version="1.0"?>
    <configuration version="32">
        <folder id=".Folder_A" label=".Folder_A" path="~/Sync/.Folder_A" type="sendreceive" rescanIntervalS="3600" fsWatcherEnabled="true" fsWatcherDelayS="10" ignorePerms="false" autoNormalize="true">
            <filesystemType>basic</filesystemType>
            <device id="123ABC" introducedBy="">
                <encryptionPassword/>
            </device>
            <device id="987ZYX" introducedBy="">
                <encryptionPassword/>
            </device>
            <minDiskFree unit="">0</minDiskFree>
            <versioning>
                    <cleanupIntervalS>0</cleanupIntervalS>
            </versioning>
            <copiers>0</copiers>
            <disableSparseFiles>false</disableSparseFiles>
            <disableTempIndexes>false</disableTempIndexes>
            <paused>false</paused>
            <weakHashThresholdPct>25</weakHashThresholdPct>
            <markerName>.stfolder</markerName>
        </folder>
        <folder id=".Folder_B" label="Corporate (.Folder_B)" path="~/Sync/.Folder_B" type="sendreceive" rescanIntervalS="3600" fsWatcherEnabled="true" fsWatcherDelayS="5" ignorePerms="true" autoNormalize="false">
            <filesystemType>basic</filesystemType>
            <device id="123ABC" introducedBy="">
                <encryptionPassword/>
            </device>
            <device id="987ZYX" introducedBy="">
                <encryptionPassword/>
            </device>
            <minDiskFree unit="">0</minDiskFree>
            <versioning>
                    <cleanupIntervalS>0</cleanupIntervalS>
            </versioning>
            <copiers>0</copiers>
            <disableSparseFiles>false</disableSparseFiles>
            <disableTempIndexes>false</disableTempIndexes>
            <paused>false</paused>
            <weakHashThresholdPct>25</weakHashThresholdPct>
            <markerName>.stfolder</markerName>
        </folder>
        <device id="123ABC" name="laptop" compression="always" introducer="false" skipIntroductionRemovals="false" introducedBy="">
            <paused>false</paused>
            <autoAcceptFolders>true</autoAcceptFolders>
            <maxSendKbps>0</maxSendKbps>
            <maxRecvKbps>0</maxRecvKbps>
            <maxRequestKiB>0</maxRequestKiB>
            <untrusted>false</untrusted>
        </device>
        <device id="987ZYX" name="desktop" compression="always" introducer="false" skipIntroductionRemovals="false" introducedBy="">
            <paused>false</paused>
            <autoAcceptFolders>true</autoAcceptFolders>
            <maxSendKbps>0</maxSendKbps>
            <maxRecvKbps>0</maxRecvKbps>
            <maxRequestKiB>0</maxRequestKiB>
            <untrusted>false</untrusted>
        </device>
        <gui enabled="true" tls="true" debugging="false">
            <address>127.0.0.1:8384</address>
            <apikey>98qewr0qe9r</apikey>
            <theme>default</theme>
        </gui>
        <ldap/>
        <options>
            <listenAddress></listenAddress>
            <maxSendKbps>0</maxSendKbps>
            <maxRecvKbps>0</maxRecvKbps>
            <reconnectionIntervalS>60</reconnectionIntervalS>
            <relaysEnabled>false</relaysEnabled>
            <relayReconnectIntervalM>10</relayReconnectIntervalM>
            <startBrowser>false</startBrowser>
            <urAccepted>-1</urAccepted>
            <urSeen>3</urSeen>
            <urUniqueID/>
            <urPostInsecurely>false</urPostInsecurely>
            <urInitialDelayS>1800</urInitialDelayS>
            <restartOnWakeup>true</restartOnWakeup>
            <upgradeToPreReleases>false</upgradeToPreReleases>
            <keepTemporariesH>24</keepTemporariesH>
            <cacheIgnoredFiles>false</cacheIgnoredFiles>
            <progressUpdateIntervalS>5</progressUpdateIntervalS>
            <limitBandwidthInLan>false</limitBandwidthInLan>
            <overwriteRemoteDeviceNamesOnConnect>false</overwriteRemoteDeviceNamesOnConnect>
            <tempIndexMinBlocks>10</tempIndexMinBlocks>
            <trafficClass>0</trafficClass>
            <defaultFolderPath>~/Sync/</defaultFolderPath>
            <maxFolderConcurrency>0</maxFolderConcurrency>
            <crashReportingEnabled>false</crashReportingEnabled>
            <databaseTuning>auto</databaseTuning>
            <maxConcurrentIncomingRequestKiB>0</maxConcurrentIncomingRequestKiB>
            <announceLANAddresses>false</announceLANAddresses>
            <sendFullIndexOnUpgrade>false</sendFullIndexOnUpgrade>
        </options>
    </configuration>

This is a config.xml example for syncthing.

Answer 1

Use the -L / --inplace option (see xmlstarlet edit --help) and the exact match from the linked answer:

xmlstarlet ed -L -d "//configuration/folder[@id=\"$foldername\"]" config.xml

Answer 2

Using xq (part of yq from https://kislyuk.github.io/yq/):

xq -x --arg id "$foldername" 'del(.configuration.folder[] | select(."@id" == $id))' config.xml

Use the -i or --in-place option to make an in-place edit.