I am having a problem extracting a substring from a string using regex.
For example I have a string like follows
str = "result[cars][ford]"
Now I need a regex which can extract out cars and ford out of that string so that when
str.match({{regex}})[1]
would provide cars and
str.match({{regex}})[2]
would provide ford
Now i need that regex inside that curly braces.
Any link that helps to this question are most welcomed.
It's actually simple.
s = "result[cars][ford]"
matches = s.scan(/\[(\w+)\]/).flatten # => ["cars", "ford"]
Here's a demo.
Related
I have a string https://stackverflow.com. I want a new string that contains the domain from the given string using regular expressions.
Example:
x = "https://stackverflow.com"
newstring = "stackoverflow.com"
Example 2:
x = "https://www.stackverflow.com"
newstring = "www.stackoverflow.com"
"https://stackverflow.com"[/(?<=:\/\/).*/]
#⇒ "stackverflow.com"
(?<=..) is a positive lookbehind.
If string = "http://stackoverflow.com",
a really easy way is string.split("http://")[1]. But this isn't regex.
A regex solution would be as follows:
string.scan(/^http:\/\/(.+)$/).flatten.first
To explain:
String#scan returns the first match of the regex.
The regex:
^ matches beginning of line
http: matches those characters
\/\/ matches //
(.+) sets a "match group" containing any number of any characters. This is the value returned by the scan.
$ matches end of line
.flatten.first extracts the results from String#scan, which in this case returns a nested array.
You might want to try this:
#!/usr/bin/env ruby
str = "https://stackoverflow.com"
if mtch = str.match(/(?::\/\/)(/S)/)
f1 = mtch.captures
end
There are two capturing groups in the match method: the first one is a non-capturing group referring to your search pattern and the second one referring to everything else afterwards. After that, the captures method will assign the desired result to f1.
I hope this solves your problem.
I have a string and I want to remove all non-word characters and whitespace from it. So I thought Regular expressions would be what I need for that.
My Regex looks like that (I defined it in the string class as a method):
/[\w&&\S]+/.match(self.downcase)
when I run this expression in Rubular with the test string "hello ..a.sdf asdf..," it highlioghts all the stuff I need ("hellloasdfasdf") but when I do the same in irb I only get "hello".
Has anyone any ideas about why that is?
Because you use match, with returns one matching element. If you use scan instead, all should work properly:
string = "hello ..a.sdf asdf..,"
string.downcase.scan(/[\w&&\S]+/)
# => ["hello", "a", "sdf", "asdf"]
\w means [a-zA-Z0-9_]
\S means any non-whitespace character [a-zA-Z_-0-9!##$%^&*\(\)\\{}?><....etc]
so using a \w and \S condition is ambiguous.
Its like saying What is an intersection of India and Asia. Obviously its going to be India. So I will suggest you to use \w+.
and you can use scan to get all matches as mentioned in the second answer :
string = "hello ..a.sdf asdf..,"
string.scan(/\w+/)
I am attempting to scan the following string with the following regular expression:
text = %q{akdce ALASKA DISTRICT COURT CM/ECFalmdce
ALABAMA MIDDLE DISTRICT COURTalndce
}
p courts = text.scan(/(ECF\w+)|(COURT\w+)/)
Ideally, what I want to do is scan the text and pull the text 'ECFalmdce' and 'COURTalndce'
With the regex I am using, I am trying to say I want a string that starts with either COURT or ECF followed by a random string of characters.
The array being returned is:
[["ECFalmdce", nil], [nil, "COURTalndce"]]
What is the deal with the nil's, does anyone have a more efficient way of writing the regex, and does anyone have a link to further documentation on match groups?
Your regex captures differently for ECF and COURT. You can create non-capture groups with ?:
text.scan(/(?:ECF|COURT)\w+/)
# => ["ECFalmdce", "COURTalndce"]
Edit
About non-capture groups: You can use them to create patterns using parenthesis without capturing the pattern.
They're patterns such as (?:pattern)
You can find more information on regular expressions at http://www.regular-expressions.info/refadv.html
Apparently I still don't understand exactly how it works ...
Here is my problem: I'm trying to match numbers in strings such as:
910 -6.258000 6.290
That string should gives me an array like this:
[910, -6.2580000, 6.290]
while the string
blabla9999 some more text 1.1
should not be matched.
The regex I'm trying to use is
/([-]?\d+[.]?\d+)/
but it doesn't do exactly that. Could someone help me ?
It would be great if the answer could clarify the use of the parenthesis in the matching.
Here's a pattern that works:
/^[^\d]+?\d+[^\d]+?\d+[\.]?\d+$/
Note that [^\d]+ means at least one non digit character.
On second thought, here's a more generic solution that doesn't need to deal with regular expressions:
str.gsub(/[^\d.-]+/, " ").split.collect{|d| d.to_f}
Example:
str = "blabla9999 some more text -1.1"
Parsed:
[9999.0, -1.1]
The parenthesis have different meanings.
[] defines a character class, that means one character is matched that is part of this class
() is defining a capturing group, the string that is matched by this part in brackets is put into a variable.
You did not define any anchors so your pattern will match your second string
blabla9999 some more text 1.1
^^^^ here ^^^ and here
Maybe this is more what you wanted
^(\s*-?\d+(?:\.\d+)?\s*)+$
See it here on Regexr
^ anchors the pattern to the start of the string and $ to the end.
it allows Whitespace \s before and after the number and an optional fraction part (?:\.\d+)? This kind of pattern will be matched at least once.
maybe /(-?\d+(.\d+)?)+/
irb(main):010:0> "910 -6.258000 6.290".scan(/(\-?\d+(\.\d+)?)+/).map{|x| x[0]}
=> ["910", "-6.258000", "6.290"]
str = " 910 -6.258000 6.290"
str.scan(/-?\d+\.?\d+/).map(&:to_f)
# => [910.0, -6.258, 6.29]
If you don't want integers to be converted to floats, try this:
str = " 910 -6.258000 6.290"
str.scan(/-?\d+\.?\d+/).map do |ns|
ns[/\./] ? ns.to_f : ns.to_i
end
# => [910, -6.258, 6.29]
I'm working on 2 cases:
assume I have those var:
a = "hello"
b = "hello-SP"
c = "not_hello"
Any partial matches
I want to accept any string that has the variable a inside, so b and c would match.
Patterned match
I want to match a string that has a inside, followed by '-', so b would match, c does not.
I am having problem, because I always used the syntax /expression/ to define Regexp, so how dynamically define an RegExp on Ruby?
You can use the same syntax to use variables in a regex, so:
reg1 = /#{a}/
would match on anything that contains the value of the a variable (at the time the expression is created!) and
reg2 = /#{a}-/
would do the same, plus a hyphen, so hello- in your example.
Edit: As Wayne Conrad points out, if a contains "any characters that would have special meaning in a regular expression," you need to escape them. Example:
a = ".com"
b = Regexp.new(Regexp.escape(a))
"blah.com" =~ b
Late to comment but I wasn't able to find what I was looking for.The above mentioned answers didn't help me.Hope it help someone new to ruby who just wants a quick fix.
Ruby Code:
st = "BJ's Restaurant & Brewery"
#take the string you want to match into a variable
m = (/BJ\'s/i).match(string) #(/"your regular expression"/.match(string))
# m has the match #<MatchData "BJ's">
m.to_s
# this will display the match
=> "BJ's"