Regex: match everything before FIRST underscore and everything in between AFTER

Question

I have an expression like

test_abc_HelloWorld_there could be more here.

1. I'd like a regex that takes the first word before the first underscore. So get "test"

I tried [A-Za-z]{1,}_ but that didn't work.

1. Then I'd like to get "abc" or anything in between the first 2 underscores.

2 Separate Regular expressions, not combined

Any help is very appreciated!

Example:

for 1) the regex would match the word test for 2) the regex would match the word abc

so any other match for either case would be wrong. As in, if I were to replace what I matched on then I would get something like this:

for case 1) match "test" and replace "test" with "Goat".

'Goat_abc_HelloWorld_there could be more here'

I don't want a replace, I just want a match on a word.

Answer 1

In both case you can use assertions.

^[^_]+(?=_)

will get you everything up to the first underscore of the line, and

(?<=_)[^_]+(?=_)

will match whatever string is located between two unserscores.

Answer 2

Step back and consider that maybe you're overengineering the solution here. Ruby has a split method for this, other languages probably have their own equivalents

given something like this "AAPL_annual_i.xls", you could just do this and take advantage of the fact that your data is already structured

string_object = "AAPL_annual_i.xls"
ary = string_object.split("_")
#=> ["AAPL", "annual", "i.xls"]
extension = ary.split(".")[1]
#=> ["xls"]
filetype = ary[3].split(".")[0] #etc

'doh!

But seriously, I've found that leaning on the split method is not only easier on me, it's easier on my associates who have to read my code and understand what it does.