How to use extract string with contains a certain pattern?

[anta40]

I'm working on a simple Instagram image downloader on Nim.

Example is this image: 
[https://www.instagram.com/p/B1oqkXKFlcD](https://www.instagram.com/p/B1oqkXKFlcD)

My idea is 1st get the HTML code of that link, like this: 
    
    
    import httpClient
    
    var client = newHttpClient()
    var src = "https://www.instagram.com/p/B1oqkXKFlcD";
    var htmlsrc = client.getContent(src)
    
    echo htmlsrc
    
    
    Run

That works fine. You'll get lots of HTML lines. The actual image itself can be 
found with the **og:image** tag: 
    
    
    <meta property="og:image" 
content="https://instagram.fcgk23-1.fna.fbcdn.net/vp/e7663a7f70afcedf1d66424a310bba19/5E13D4FF/t51.2885-15/e35/p1080x1080/67664270_675154659649319_4991162461801475991_n.jpg?_nc_ht=instagram.fcgk23-1.fna.fbcdn.net&_nc_cat=111";
 />
    
    
    Run

Now, how can I extract the link: 
[https://instagram.fcgk23-1.fna.fbcdn.net/vp/e7663a.....](https://instagram.fcgk23-1.fna.fbcdn.net/vp/e7663a.....)
 ? Once I do that, then I can pass it to a image downloading function.