How to search web pages by keywords?

Question

Search engines

Hello. It is necessary to implement a service that would collect media messages for a specific request (for example, media messages about the actions of an organization). I roughly imagine the process of parsing a certain page, but how to get these very pages from the network for certain keywords? I found many similar services, for example, Webhose, but how to implement it on my own? Data must be collected from open media resources and social networks. At the output, you need to get the text for further analysis. Tell me in which direction to move, mb someone knows the relevant literature?