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Is there a command line tool that can remove comments from an XML file? Or do I need to write a small program that makes use of an XML parser to do this?

Update: I'm not interested in solutions that only handle a subset of all possible XML files.

For instance a regexp can't handle XML parsing.

https://stackoverflow.com/questions/6751105/why-its-not-possible-to-use-regex-to-parse-html-xml-a-formal-explanation-in-la

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3 Answers 3

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18

I would do it in this way:

cat myfile.xml | sed '/<!--.*-->/d' | sed '/<!--/,/-->/d' > cleaned.xml

Or:

awk 'in_comment&&/-->/{sub(/([^-]|-[^-])*--+>/,"");in_comment=0}
 in_comment{next}
 {gsub(/<!--+([^-]|-[^-])*--+>/,"");
  in_comment=sub(/<!--+.*/,"");
  print}'

Or: 

xmlstarlet ed -d '//comment()' file.xml
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    I know regex solutions can't handle XML parsing (without possible errors). But I guess the third solution is using a real XML parser under the hood?
    – Erik Sjölund
    Sep 19, 2014 at 11:07
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    Erik, yes, xmlstarlet is designed for xml manipulation.
    – Frantique
    Sep 19, 2014 at 11:26
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    Ok, I checked. xmlstarlet uses libxml2. If you remove the first sed and awk suggestions that are not correct according to me, I'll accept the xmlstarlet suggestion as the accepted answer.
    – Erik Sjölund
    Sep 19, 2014 at 12:04
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    it's disappointing to know that none of the big editors (Sublime, vim, Atom, Notepad++) have this feature built-in. Sad, sad, sad. Thanks @Frantique
    – Lucas Pottersky
    Jun 28, 2016 at 18:52
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    I would like to keep only comments that contain "TODO" on it, any idea if possible with xmlstarlet?
    – Aquarius Power
    Jul 25, 2022 at 0:20
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To expand on the top answer. If you only want to delete the comment and not the entire line, you should probably use:

sed 's/<!--.*-->//'

In my case, I had a minified XML file where the entire content was in a single line and since the previous solution would delete the entire line where the comment was located, it would completely clear out my file.

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  • Quote from the question "I'm not interested in solutions that only handle a subset of all possible XML files.". The difficult thing is finding a solution that can handle all XML files, not just a subset.
    – Erik Sjölund
    May 30, 2022 at 13:42
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This is good to clean multiline comments (like failed tests) from a xml, least the ones you hand picked and are helpful to the end user:
perl -i -w -0777pe 's/<!--(.(?<!(HELP|TODO)))*?-->//sg' somefile.xml

more about related regex: https://stackoverflow.com/a/1240293/1422630

If there is a way to obtain the same result but using xmlstarlet, I would prefer as there may have some exception that regex may not handle, but for now this is what I have to use.

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