how to use a regular expression to extract json fields?

Question

Beginner RegExp question. I have lines of JSON in a textfile, each with slightly different Fields, but there are 3 fields I want to extract for each line if it has it, ignor

Answer 1

Why does it have to be a Regular Expression object?

Here we can just use a Hash object first and then go search it.

mh = {"url":"http://www.netcharles.com/orwell/essays.htm","domain":"netcharles.com","title":"Orwell Essays & Journalism Section - Charles' George Orwell Links","tags":["orwell","writing","literature","journalism","essays","politics","essay","reference","language","toread"],"index":2931,"time_created":1345419323,"num_saves":24}

The output of which would be

=> {:url=>"http://www.netcharles.com/orwell/essays.htm", :domain=>"netcharles.com", :title=>"Orwell Essays & Journalism Section - Charles' George Orwell Links", :tags=>["orwell", "writing", "literature", "journalism", "essays", "politics", "essay", "reference", "language", "toread"], :index=>2931, :time_created=>1345419323, :num_saves=>24}

Not that I want to avoid using Regexp but don't you think it would be easier to take it a step at a time until your getting the data you want to further search through? Just MHO.

mh.values_at(:url, :title, :tags)

The output:

["http://www.netcharles.com/orwell/essays.htm", "Orwell Essays & Journalism Section - Charles' George Orwell Links", ["orwell", "writing", "literature", "journalism", "essays", "politics", "essay", "reference", "language", "toread"]]

Taking the pattern that FrankieTheKneeman gave you:

pattern = /"(url|title|tags)":"((\\"|[^"])*)"/i

we can search the mh hash by converting it to a json object.

/#{pattern}/.match(mh.to_json)

The output:

=> #

Of course this is all done in Ruby which is not a tag that you have but relates I hope.

But oops! Looks like we can't do all three at once with that pattern so I will do them one at a time just for sake.

pattern = /"(title)":"((\\"|[^"])*)"/i

/#{pattern}/.match(mh.to_json)

#

pattern = /"(tags)":"((\\"|[^"])*)"/i

/#{pattern}/.match(mh.to_json)

=> nil

Sorry about that last one. It will have to be handled differently.