How to use sed to extract substring

Question

I have a file containing the following lines:

  
  &         


        

Answer 1

sed 's/[^"]*"\([^"]*\).*/\1/'

does the job.

explanation of the part inside ' '

• s - tells sed to substitute
• / - start of regex string to search for
• [^"]* - any character that is not ", any number of times. (matching parameter name=)
• " - just a ".
• ([^"]*) - anything inside () will be saved for reference to use later. The \ are there so the brackets are not considered as characters to search for. [^"]* means the same as above. (matching RemoteHost for example)
• .* - any character, any number of times. (matching " access="readWrite"> /parameter)
• / - end of the search regex, and start of the substitute string.
• \1 - reference to that string we found in the brackets above.
• / end of the substitute string.

basically s/search for this/replace with this/ but we're telling him to replace the whole line with just a piece of it we found earlier.