Use sed to insert a character in an xml file

Question

I have an xml file with content following this format:

<type:color>000000</type:color> <type:color>FFFFFF</type:color> 

The information within the tags are hex colors (many different colors), but they need to begin with a pound sign (#) to work in a particular application, ie:

<type:color>#000000</type:color> <type:color>#FFFFFF</type:color> 

How can I use sed to append the pound symbol in this file? Using sed 4.8 BTW, thanks!

Answer 1

This looks to be pretty simple:

cat - << EOF | <type:color>000000</type:color> <type:color>FFFFFF</type:color> EOF sed 's/<type:color>/<type:color>#/' 

Or just:

sed 's/<type:color>/&#/' 

Where the & character is a placeholder for the text that matched.

To add that # only if it wasn't there already:

sed 's/\(<type:color>\)\([^#]\)/\1#\2/' 

More legible if your sed supports -E for Extended regexps:

sed -E 's/(<type:color>)([^#])/\1#\2/' 

Or:

sed -E 's/(<type:color>)#?/\1#/' 

Answer 2

Assuming a well-formed XML document, like this:

<?xml version="1.0"?> <root xmlns:type="uri://something/type"> <type:color>000000</type:color> <type:color>FFFFFF</type:color> </root> 

... we may use e.g. xmlstarlet to update all values of all type:color nodes in the whole document, inserting a # character at the start of each:

xmlstarlet ed -u '//type:color' -x 'concat("#", text())' file 

or, using longer names,

xmlstarlet edit \ --update '//type:color' \ --expr 'concat("#", text())' \ file 

Result:

<?xml version="1.0"?> <root xmlns:type="uri://something/type"> <type:color>#000000</type:color> <type:color>#FFFFFF</type:color> </root>