String::gsub catch a group and use it

Help & Support
1

Hi guys, I try to do something, but like usual, I am not good with regex :smiling_face_with_tear:

Basically, I would like with a regex to catch all texts starting with a $ (uppercase only or containing as well number), and replace it by ENV[“textvalue”]

Example:

puts "/usr/bin:$PATH:/usr/share:$NUT".gsub(/(\$)([A-Z0-9])\w+/,"ENV[\"\1\"]")

Expected result:
/usr/bin:ENV["PATH"]:/usr/share:ENV["NUT"]

2 
puts "/usr/bin:$PATH:/usr/share:$NUT".gsub(/\$([A-Z0-9]+)/,"ENV[\"\\1\"]")

Seems to do the trick.

1 Like
3

Thanks a lot !

4

And when the regex catch the environment variable, if I want to replace by the value of that var in the system ?

I tried that but don’t work:

puts "/usr/bin:$PATH1:/usr/share:$NUT".gsub(/\$([A-Z0-9]+)/,"#{ENV["\\1"]}")
5

You’d probably want to use the block version of #gsub in that case, so you can access the match group for each ENV var:

"/usr/bin:$PATH1:/usr/share:$NUT".gsub(/\$([A-Z0-9]+)/) do |_, match|
    ENV[match[1]]
  end
1 Like
6

Thanks a lot. It’s exactly what I need

7

Just want to mention: https://rubular.com :)

It’s been my goto website for building and testing regular expressions, ever since I was introduced to Ruby back in 2009.

8

Crystal uses a different Regex engine than Ruby, so it might not be the best option for testing Crystal regexes. I usually use https://regexr.com/, but be sure to change the engine to PCRE instead of Javascript as it defaults to towards the top right.