Question

I want to search for a pattern and append to that in a file.

To be precise here is an example of my pattern and there are hundreds in a file.

         <size>30</size> needs to be replaced with <size>30,-1</size>

But the number in place of 30 is a variable (it can be any number from 0-99)

I am new to sed but I have used sed with known patterns but dont know how to modify when there is a variable in the pattern.

also I saw a sample where the code is placed in .sed file

      for example: sed replace.sed datafile.xyz > new.xyz 

how do I achieve that?

Thanks

Answer 1

With sed you can store part of the matched text with parentheses and include it in the replacement:

http://www.grymoire.com/Unix/Sed.html#uh-4

So, for example:

sed 's:<size>\([0-9][0-9]*\)</size>:<size>\1,-1</size>:g' ...