Retrieving Value from XML using grep and regular expressions - regex

Question

I have the below response being returned from my build system. The build generates multiple artifacts and I want to extract the link to particular artifact from the response below. Let us say something.exe.
<Artifacts>
<artifact name="artifact1" version="1.0" buildId="13321123" make_target="beta" branch="branchName" date="2017-04-21 00:31:38.74856-07"
endtime="2017-04-21 00:59:54.680601-07"
status="succeeded"
change="e850b01967222464ffca02bf94dc711236fa978a"
released="no">
<file url="http://build.system.org/path/to/artifact/folder/MD5SUM.txt"/><file url="http://build.system.org/path/to/artifact/folder/SHA1SUM.txt"/><file url="http://build.system.org/path/to/artifact/folder/SHA256SUM.txt"/><file url="http://build.system.org/path/to/artifact/folder/something.exe"/><file url="http://build.system.org/path/to/artifact/folder/something_x64.msi"/>
</artifact>
</Artifacts>
I would like to know a way to extract just the URL for something.exe. I have tried using piping the curl output and run a grep -E with a regular expression but that gives me the entire line instead.
curl -s --request GET http://build.system.org/path/to/artifact/folder/api/?build=13321123 | grep -E 'file url='
curl -s --request GET http://build.system.org/path/to/artifact/folder/api/?build=13321123 | | grep -E 'file url="http\S+OVF10.ova"'
Is there a way to just extract the following ?
http://build.system.org/path/to/artifact/folder/something.exe

Answer 1

The righteous way would be to use XML tools in this case, such as xmlstarlet
But that, of course, requires a valid XML structure. A valid XML structure would look like:
<artifact name="artifact1" version="1.0" buildId="13321123" make_target="beta" branch="branchName" date="2017-04-21 00:31:38.74856-07"
endtime="2017-04-21 00:59:54.680601-07"
status="succeeded"
change="e850b01967222464ffca02bf94dc711236fa978a"
released="no">
<file url="http://build.system.org/path/to/artifact/folder/MD5SUM.txt"/><file url="http://build.system.org/path/to/artifact/folder/SHA1SUM.txt"/><file url="http://build.system.org/path/to/artifact/folder/SHA256SUM.txt"/><file url="http://build.system.org/path/to/artifact/folder/something.exe"/><file url="http://build.system.org/path/to/artifact/folder/something_x64.msi"/>
</artifact>
The command:
xmlstarlet sel -t -v "//artifact/file[contains(#url,'something.exe')]/#url" -n xmlfile
The output:
http://build.system.org/path/to/artifact/folder/something.exe
-v option (or --value-of ) - print value of XPATH expression
The XPATH contains() function returns true if the first argument string contains the second argument string, and otherwise returns false.

Answer 2

As RomanPerekhrest said, use an xml parser for this kind of task. For your example input you could use xmlstarlet like this:
xml sel -t -m 'Artifacts/artifact/file [contains(#url, "something.exe")]' -v #url
Output:
http://build.system.org/path/to/artifact/folder/something.exe

Answer 3

This regex should work: ([\w\d\s]*.exe)"\/> (it searches for a string that consists of (/somename.exe"/> , where someonemae must consist of letters, digits, or basic space signs ("_","-"," ").
$ regex="([\w\d\s]*.exe)"\/>"
$ echo $input | grep -oP "$regex"
Though, as someone mentioned above, you shouldn't use regex to parse xml, use xml parsers.