How to replace multiple xml lines with bash

Question

I'm New in bash scripting.

I have xml tabs in file alpha.xml, as

<tab>
<enabled>false</enabled>
</tab>
<tabToChange>
<enabled>false</enabled>
</tabToChange >

I'm trying to change this to

<tab>
<enabled>false</enabled>
</tab>
<tabToChange>
<enabled>true</enabled>
</tabToChange >

referencing with https://unix.stackexchange.com/questions/26284/how-can-i-use-sed-to-replace-a-multi-line-string

I tried command as

sed '/^tabToChange$/ {N; s/\<tabToChange\>n\<enabled\>/yo/g}' alpha.txt
sed '/^\<<tabToChange>\>$/ {N; s/\<<tabToChange>\>\n\<enabled\>/yo/g}' alpha.txt
sed '/^\<\<tabToChange\>\>$/ {N; s/\<\<tabToChange\>\>\n\<\<enabled\>\>/yo/g}' alpha.txt

None of them works. Could someone please help me

show the parent tag which contains those you have posted. I mean there should the "root" tag for valid xml structure — RomanPerekhrest, May 05 '17 at 17:14
Concur with @123, any regex-based approach is likely to be hit-or-miss. Some nice command-line xml tool recommendations here: http://stackoverflow.com/questions/91791/grep-and-sed-equivalent-for-xml-command-line-processing — Vasan, May 05 '17 at 17:21

score 2 · Answer 1 · answered May 05 '17 at 17:26

To manipulate XML documents use XML parsers/tools.
I would use xmlstarlet tool. Supposing that input XML data is enclosed in parent <root> tag (you'll have your own tag):

<root>
<tab>
<enabled>false</enabled>
</tab>
<tabToChange>
<enabled>false</enabled>
</tabToChange >
</root>

The command:

xmlstarlet ed -u "//tabToChange/enabled" -v true alpha.xml

The output:

<?xml version="1.0"?>
<root>
  <tab>
    <enabled>false</enabled>
  </tab>
  <tabToChange>
    <enabled>true</enabled>
  </tabToChange>
</root>

ed - edit mode

-u - to update value

"//tabToChange/enabled" - xpath expression to match the needed element

-v true - the value to be set

score 0 · Answer 2 · answered May 05 '17 at 17:25

I agree with the recommendation to use an appropriate tool. But just for the fun of sed:

sed  "/tabToChange/{N;s/\(tabToChange>\n<enabled>\)false\(<\/enabled>\)/\1true\2/;}" alpha.txt

be careful with the < and >
keep the \n in mind you get when appending N

berrytchaks · Accepted Answer · 2017-05-08T18:58:47.487

You can do that with the following commands.

cat alpha.xml | tr '\n' '\f' | sed -e '0,/<tab>\f<enabled>false<\/enabled>\f<\/tab>\f<tabToChange>\f<enabled>false<\/enabled>\f<\/tabToChange >/s//<tab>\f<enabled>false<\/enabled>\f<\/tab>\f<tabToChange>\f<enabled>true<\/enabled>\f<\/tabToChange >/'  | tr '\f' '\n' > alpha1.xml
cp alpha1.xml alpha.xml
rm alpha1.xml

Make that you respect space before any line your want to replace. That is if we have

<tab>
    <enabled>false</enabled>
</tab>
<tabToChange>
    <enabled>false</enabled>
</tabToChange >

That we want to replace with

<tab>
    <enabled>false</enabled>
</tab>
<tabToChange>
    <enabled>true</enabled>
</tabToChange >

The commands to use are:

cat alpha.xml | tr '\n' '\f' | sed -e '0,/<tab>\f    <enabled>false<\/enabled>\f<\/tab>\f<tabToChange>\f    <enabled>false<\/enabled>\f<\/tabToChange >/s//<tab>\f    <enabled>false<\/enabled>\f<\/tab>\f<tabToChange>\f    <enabled>true<\/enabled>\f<\/tabToChange >/'  | tr '\f' '\n' > alpha1.xml
cp alpha1.xml alpha.xml
rm alpha1.xml

Notice that we respect the 4 tabs that come before the <enabled>false</enabled>.

How to replace multiple xml lines with bash

3 Answers3