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I am trying to add field at the end of tag using sed script. Suppose I have a tag in XML file:

<book name="Sed tutorial" price="250"/>

Now I want to add field as Book_Width="A" after end of <book/> tag so that my tag becomes:

<book name="Sed tutorial" price="250" Book_Width="A"/>

I tried with sed:

sed '/<book "[^>]*>/ a Book_Width="A"'

but it gives:

<book name="Sed tutorial" price="250"/>
Book_Width="A"
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Related :) –  Kroltan 10 hours ago

3 Answers 3

up vote 10 down vote accepted

You should not parse xml with sed, use an xml parser like xmlstarlet instead. For your task it would be:

xmlstarlet ed -O --inplace --insert "/book" --type attr -n Book_Width -v A xml_file

The file content is then:

<book name="Sed tutorial" price="250" Book_Width="A"/>
  • The ed means edit mode to edit the xml tree
  • -O omits the xml tag
  • We want to insert something with --insert
  • "/book" is the path where to insert
  • --type attr: it's an attribute, we want to insert
  • The name -n of the attribute
  • The value -v
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can I update xml_file rather printing its output –  krishna 14 hours ago
    
@krishna Yes with --inplace I added it to my answer –  chaos 14 hours ago
up vote 3 down vote

in sed "a" appends a pattern IN A NEW LINE.

what you want to do is replace (substitute). Let's use a colon as separator for clarity:

sed 's:\(<book.*\)\(/>\):\1 Book_Width="A"\2:'

anything in \( .. \) is a pattern memorized by the order of appearance and recalled by \indexnumber , e.g. \1 will reproduce the first pattern saved.

So we are memorizing <book name="Sed tutorial" price="250" as pattern 1 and /> as pattern 2 and just insert Book_Width="A" in the middle.

echo '<book name="Sed tutorial" price="250"/>' | sed 's:\(<book.*\)\(/>\):\1 Book_Width="A"\2:'
<book name="Sed tutorial" price="250" Book_Width="A"/>
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up vote 1 down vote

With awk you can do something like this:

Supposing the line is in file file1.xml then:

awk -F '/' '{print $1,"Book_Width=\"A\"",FS,$2}' file1.xml
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This is not checking that the tag is "book" –  glenn jackman 11 hours ago

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