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I want to extract the contents of fqdns from the following file, but only for each device where status is new:

<device id='10.72.48.215'>
    <address>10.72.48.215</address>
    <status>old</status>
    <fqdns>10.72.48.215</fqdns>
    <parent></parent>
    <type>Unknown</type>
    <ports>
    </ports>
    <operatingsystems>
    </operatingsystems>
</device>
<device id='10.72.48.216'>
    <address>10.72.48.216</address>
    <status>new</status>
    <fqdns>10.72.48.216</fqdns>
    <parent></parent>
    <type>Unknown</type>
    <ports>
    </ports>
    <operatingsystems>
    </operatingsystems>
</device>

So, for the above, I want to obtain 10.72.48.216 (and not 10.72.48.215).

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  • 2
    Can you provide the output you want to extract from this xml file? I don't understand which part you mean. Commented Dec 8, 2015 at 15:57
  • 1
    I do not understand it too, Commented Dec 8, 2015 at 15:57
  • 1
    so basically, i have this long xml file with the same contents as above. some have "<status>old</status>" some has "new". But i just want to grab the "new" one. " <status>new</status> <fqdns>10.72.48.151</fqdns> <status>new</status> <fqdns>10.72.48.152</fqdns> <status>new</status> <fqdns>10.72.48.153</fqdns>" something like so Commented Dec 8, 2015 at 16:00
  • Your example has only old ones. Commented Dec 8, 2015 at 16:05
  • pcregrep -M "\<status.*\n.*fqdns\>$" file.xml Commented Dec 8, 2015 at 16:06

3 Answers 3

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3

If you add an XML declaration and enclose the two device elements in a top-level element, you can process your file with XPath: 

$ cat ./248127.xml
    <device id='10.72.48.215'>
            <address>10.72.48.215</address>
            <status>old</status>
            <fqdns>10.72.48.215</fqdns>
            <parent></parent>
            <type>Unknown</type>
            <ports>
            </ports>
            <operatingsystems>
            </operatingsystems>
    </device>
    <device id='10.72.48.216'>
            <address>10.72.48.216</address>
            <status>new</status>
            <fqdns>10.72.48.216</fqdns>
            <parent></parent>
            <type>Unknown</type>
            <ports>
            </ports>
            <operatingsystems>
            </operatingsystems>
    </device>

$ ( echo '<?xml version="1.0"?><doc>'; cat ./248127.xml ; echo '</doc>' ) \
    | xpath -q -e '//device[status/text()="new"]/fqdns'
<fqdns>10.72.48.216</fqdns>
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  • Toby, how i have both "old" and "new" status in the file. How do I just get the "new" one? Commented Dec 8, 2015 at 16:17
  • Modify the XPath expression appropriately - e.g. xpath -q -e '//device[status/text()="new"]/fqdns' Commented Dec 8, 2015 at 16:34
  • thxs this also works Commented Dec 8, 2015 at 18:30
1

You can do it with a pcrgrep command, which has an option for multiline search.

pcregrep -M "\<status.*\n.*fqdns\>$"

As for the explanation you requested:

So -M for multiline

\< status for the beggining of string. I have to use \ to take the meaning out of < as it is special to the shell.

Then . (any character) followed by * with it means it can be repeated.

\n for a new line

. for a character followed by * as it can be repeated.

then the string fqdns

and to close

\> which again is >, with \ to take the meaning

and finally, $ is the end of line

The strings matching is know as regexp

https://en.wikipedia.org/wiki/Regular_expression

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  • You are welcome. Please peruse the wikipedia entry to be able to build your own regexp expressions. Commented Dec 8, 2015 at 16:23
1

A simple grep can do the trick:

grep -A1 "<status>new" sample.xml 
# <status>new</status>
# <fqdns>10.72.48.216</fqdns>

which is only recommendet if the source of your xml is stable and doesn't change the order of lines. (I modified your example to have a 'new' in the second block.)

You may filter the following line with more grep:

grep -A1 "<status>new" sample.xml | grep "<fqdns>" 
# <fqdns>10.72.48.216</fqdns>

With sed, you can easily extract just the IP:

sed -rn '/<status>new/{n; s/.*<fqdns>(.*)<\/fqdns>/\1/p}' sample.xml
# 10.72.48.216

It matches <status>new and reads the next line and substitutes <fqdns> and the end tag with the part in betweeen. The -n tells sed to 'no printing by default', the '-r' is to allow regular expressions, here the parens around .*, to be written without masking.

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  • This is awesome. this is exactly what I needed. Thanks Commented Dec 8, 2015 at 16:27

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