Adding XML element in XML file using sed command in shell script

Question

I am using sed command to insert an xml element into the existing xml file.

I have xml file as

Answer 1

You cannot have an unescaped newline in sed replacement text, that is $CONTENT in your example. sed uses the newline just like the shell does, to terminate a command.

If you need a newline in the replacement text, you need to precede it with a backslash.

There is another way to add text using the r option. For example:

Lets say your main file is;

$ cat file
<Students>
    <student>
        <name>john</>
        <id>123</id>
    </student>
    <student>
        <name>mike</name>
        <id>234</id>
    </student>
</Students>

You text you want to add is in another file (not variable):

$ cat add.txt
    <student>
        <name>NewName</name>
        <id>NewID</id>
    </student>

You can do (using gnu sed):

$ sed '/<\/Students>/{ 
    r add.txt
    a \</Students>
    d 
}' file
<Students>
    <student>
        <name>john</>
        <id>123</id>
    </student>
    <student>
        <name>mike</name>
        <id>234</id>
    </student>
    <student>
        <name>NewName</name>
        <id>NewID</id>
    </student>
</Students>

However, having given this option, it is still a very bad idea to parse xml with regular expression. It makes the solution very fragile and easy to break. Consider this as a learning exercise only.

Answer 2

This might work for you (GNU sed & Bash):

CONTENT='    <student>\
    <name>NewName</name>\
    <id>NewID</id>\
</student>'

sed '/<\/Students>/i\'"$CONTENT" file

Alternatively, put the new students in a file and:

sed '/<\/Students>/e cat new_student_file' file

Answer 3

change this:

CONTENT="<student>
            <name>NewName</name>
            <id>NewID</id>
        </student>"

to this:

CONTENT="<student>\n<name>NewName</name>\n<id>NewID</id>\n</student>"

and then:

C=$(echo $CONTENT | sed 's/\//\\\//g')
sed "/<\/Students>/ s/.*/${C}\n&/" file