Ruby regex to extract match_group value? - ruby

Question

I have two questions about regex.
The match string is:
"FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA, user_email=admin#example.com"
When extracting the user_email value, my regexp is:
\s+(?<email_from_header>\S+)
and the match group value is:
(space)user_email=admin#example.com"
What do I use to omit the first (space) char and the last " quote?
When extracting the token, my regex is:
AUTH-TOKEN\s+(?<auth_token>\S+)
and the match group value is:
FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA,
What do I use to delete that last trailing comma ,?

Answer 1

Your regex would be,
\s+\K(?<email_from_header>[^"]*)
Use \K switch to discard the previously matched characters. And use not character class to match any character not of " zero or more times.
Your regex would be,
AUTH-TOKEN\s+(?<auth_token>[^,]*)
[^,]* it would match any character not of , zero or more times.

Answer 2

If your string has embedded double-quotes:
str[/^"(.+),/, 1] # => "FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA"
str[/^"(.+?),/, 1] # => "FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA"
str[/^"([^,]+),/, 1] # => "FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA"
str = '"FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA, user_email=admin#example.com"'
str # => "\"FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA, user_email=admin#example.com\""
str[/(user_email=.+)"/, 1] # => "user_email=admin#example.com"
str[/(user_email=[^"]+)"/, 1] # => "user_email=admin#example.com"
str[/user_email=([^"]+)"/, 1] # => "admin#example.com"
match = str.match(/(?<user_email>user_email=(?<addr>.+))"/)
match # => #<MatchData "user_email=admin#example.com\"" user_email:"user_email=admin#example.com" addr:"admin#example.com">
match['user_email'] # => "user_email=admin#example.com"
match['addr'] # => "admin#example.com"
If it doesn't:
str = 'FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA, user_email=admin#example.com'
str # => "FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA, user_email=admin#example.com"
str[/^(.+),/, 1] # => "FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA"
str[/^(.+?),/, 1] # => "FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA"
str[/^([^,]+),/, 1] # => "FuR6UcUiduzPyenxCSzZbDXTge3f3t9ufA"
str[/(user_email=.+)/, 1] # => "user_email=admin#example.com"
str[/(user_email=(.+))/, 2] # => "admin#example.com"
str[/user_email=(.+)/, 1] # => "admin#example.com"
Or, having more regex fun:
match = str.match(/(?<user_email>user_email=(?<addr>.+))/)
match # => #<MatchData "user_email=admin#example.com" user_email:"user_email=admin#example.com" addr:"admin#example.com">
match['user_email'] # => "user_email=admin#example.com"
match['addr'] # => "admin#example.com"
Regular expressions are a very rich language, and you can write something in many ways usually. The problem then becomes maintaining the pattern as the program "matures". I recommend starting simply, and expanding the pattern as the needs dictate. Don't start complex hoping to find a working solution, because that usually doesn't work; Getting a complex pattern to work immediately often fails.