Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 9 years ago.
Improve this question
I need to validate version numbers, e.g., 6.0.2/6.0.2.011 when a user enters them.
I checked to_i, but it doesn't serve my purpose. What can be a way to validate the version number? Can anyone let me know?
Here's a regular expression that matches a "valid" version number as per your specifications (only numbers separated by .):
/\A\d+(?:\.\d+)*\z/
This expression can be broken down as follows:
\A anchor the expression to the start of the string
\d+ match one or more digit character ([0-9])
(?: begin a non-capturing group
\. match a literal dot (.) character
\d+ match one or more digit character
)* end the group, and allow it to repeat 0 or more times
\z anchor the expression to the end of the string
This expression will only allow . when followed by at least one more number, but will allow any number of "sections" of the version number (ie. 6, 6.0, 6.0.2, and 6.0.2.011 will all match).
If you want to work with version numbers, I advise the versionomy (Github) gem.
See if this helps.
if a.length == a.scan(/\d|\./).length
# only dots and numbers are present
# do something
else
# do something else
end
e.g
a = '6.0.2.011'
a.length == a.scan(/\d|\./).length #=> true
b = '6b.0.2+2.011'
b.length == b.scan(/\d|\./).length #=> false
input length is checked against the scan outcome's length to ensure only dot and numbers are present. Having said that, it is very hard to guarantee that future version numbers will all follow the same conventions. How will you make sure that some one does not introduce something like 6a.0.2.011
Related
Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 3 years ago.
Improve this question
please is in ruby possible to get information from example name "Doe,Jon" (exact format) to get only the name "Jon"? Of course the name can be always different, I was thinking if is not possible to get the value from end of string to "," separator. If is it possible, how?
Thanks for your help.
So lets examine some of the solutions that are given to you in the comments
Split
"Doe,Jon".split(',').last
# or a bit more verbose
parts = "Doe,Jon".split(',') # ["Doe", "Jon"]
name = parts.last # "Jon"
String#split splits a sting into an array. It uses the parameter "," as separator. Array#last returns the last item from an array.
Gsub
"Doe,Jon".gsub(/.*,/, '')
String#gsub substitutes the part that matches the Regular Expression (/.*,/) with the substitution value ("").
The regexp matches everything (.*) up to (and including) the comma. And the replacement is an empty string, essentially deleting the part that matches the regexp.
Note that you could/should probably have an anchor to make the regexp more strict (/\A.*,/)
Slice
String#slice creates a substring given a range. -1 is a shortcut for the last element.
String#index finds the index of a character inside a String.
"Doe,Jon".slice(("Doe,Jon".index(',')+1)..-1)
# or more verbose
full = "Doe,Jon"
index_of_comma = full.index(',') # => 3
index_after_comma = index + 1
name = full.slice(index_after_comma..full.size)
CSV
CSV (Comma Separated Values) is a format where multiple values are separated by a comma (or other separation character).
require "csv"
CSV.parse("John,Doe")[0][1]
This will treat the name as CSV data and then access the first row of data (´[0]´). And from that row accesses the second element ([1]) which is the name.
Now what?
There are usually multiple ways to reach a goal. And it's up to you to pick a way. I'd go with the first one. To me it is easy to read and understand its purpose.
Closed. This question is opinion-based. It is not currently accepting answers.
Want to improve this question? Update the question so it can be answered with facts and citations by editing this post.
Closed 4 years ago.
Improve this question
This is my attempt, is there a better way?
^([2-9]|[1-9][0-9]|100)$
The better way could be not to use regex.
puts 'in range' if (2..100) === '20'.to_i
You regex is not correct for Ruby. In Ruby, ^ matches at the beginning of a line, not the beginning of the string; similarly for $ at the end of line not string.
In Ruby, ^ and $ are almost always a mistake, you generally want to use \A and \z (respectively) instead:
\A([2-9]|[1-9][0-9]|100)\z
If you want or need to use a regex, start with a regex that matches what you're looking for.
It depends.
If that regex is just a piece of a bigger regexp or the regexp is kind of a parameter for passing to a function that just accepts a regexp then I don't think It can be better than that.
However, if you just use this for validating some numbers, then a much better approach is to cast the text to an integer a then validate with >= 2 and <=100 or between?
It depends on what your context is and if you are concerned about performance.
I would do conversion to int:
str =~ /^(\d+)$/ && $1.to_i.between?(2, 100)
I think it is much easier to read than your regex. Basically, it says: "str is just a number and this number is between 2 and 100".
And this test is fully compatible with yours (equivalent)
Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 7 years ago.
Improve this question
i am constructing a program in Ruby which requires the value to be extracted between the 2nd and 3rd full-stop in a string.
I have searched online for various related solutions, including truncation and this prior Stack-Overflow question: Get value between 2nd and 3rd comma, however no answer illustrated a solution in the Ruby language.
Thanks in Advance.
list = my_string.split(".")
list[2]
That will do it I think. First command splits it into a list. Second gets the bit you want
You could split the string on full stops (aka periods), but that creates an array with one element for each substring preceding a full stop. If the document had, say, one million such substrings, that would be a rather inefficient way of getting just the third one.
Suppose the string is:
mystring =<<_
Now is the time
for all Rubiests
to come to the
aid of their
bowling team.
Or their frisbee
team. Or their
air guitar team.
Or maybe something
else...
_
Here are a couple of approaches you could take.
#1 Use a regular expression
r = /
(?: # start a non-capture group
.*?\. # match any character any number of times, lazily, followed by a full stop
){2} # end non-capture group and perform operation twice
\K # forget everything matched before
[^.]* # match everything up to the next full stop
/xm # extended/free-spacing regex definition mode and multiline mode
mystring[r]
#=> " Or their\nair guitar team"
You could of course write the regex:
r = /(?:.*?\.){2}\K[^.]*/m
but the extended form makes it self-documenting.
The regex engine will step through the string until it finds a match or concludes that there can be no match, and stop there.
#2 Pretend a full stop is a newline
First suppose we were looking for the third line, rather than the third substring followed by a full stop. We could write:
mystring.each_line.take(3).last.chomp
# => "to come to the"
Enumerable#take determines when a line ends by examining the input record separator, which is held by the global variable $/. By default, $/ equals a newline. We therefore could do this:
irs = $/ # save old value, normally \n
$/ = '.'
mystring.each_line.take(3).last[0..-2]
#=> " Or their\nair guitar team"
Then leave no footprints:
$/ = irs
Here String#each_line returns an enumerator (in effect, a rule for determining a sequence of values), not an array.
Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 7 years ago.
Improve this question
I have a regex that looks for certain types of hostnames like: .*-.*(nmtg)*|.*(\.nms). How do I modify this so it does not match: 11.22:33:44:55-66?
Should match:
cs25-admin.nmtg.company.com
cs25-admin
but should not match:
11.22:33:44:55-66
Two basic ways:
You can replace your "match anything" . with "match anything except for colon" [^:] everywhere
You can prepend your expression with "no colons from here to the end of string" (?!.*:)
EDIT As Signus said, your regexp is really non-specific and open-ended; it will match much more than what you think. For example, "----THRICEnmtgnmtgnmtg" is a full match, and so is "(-_-)". It is a better policy and easier to carefully specify what you want, rather than go listing exceptions. The regexps suggested by Signus are a good example.
They will still match within strings: "dont match this: example.com" will still match the "example.com" part. If that is what you want, cool. If not, you want to anchor the start and end of the string, by surrounding your regexp with /^.....$/.
You're using the * quantifier that matches 0 or more of the preceding token, in which case you supplied . which is a token that matches any character except line breaks.
To match domain names with subdomain names you can do the following:
(\w+\.)?\w+\.(com|org)
And to really match any domain with a TLD I like to do this:
([a-zA-Z0-9]+\.){1,2}[a-zA-Z]{2,4}
Where the latter will match any domain with a single subdomain using the numeric quantifer {num} which allows you to specify a range of matches, as shown in the above regex.
This allows you to match a group of alphanumeric characters followed by a period 1 to 2 times (i.e. subdomain.domain.topleveldomain, where subdomain. is the first match and domain. is the second match of the first group).
Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 8 years ago.
Improve this question
I would like to start a new line after every 66 characters for any file that is input into a Ruby script.
some_string.insert( 66, "\n" )
puts some_string
shows that a new line starts after the 66th character but I need it to happen after each 66th character. In other words, each line should be 66 characters long (except possibly the last).
I'm sure it involves a regex but I've tried various with insert, scan, gsub and cannot get it to work.
I'm new to Ruby and programming and this is the first thing I've tried outside of a tutorial. Thanks for the information, all.
You could do something like this:
<your_string>.scan(/.{1,66}/).join("\n")
It will basically split <your_string> at every 66th character and then re-join it by adding the \n between each part.
Or this variation to not split words in half:
<your_string>.scan(/.{1,66} /).join("\n")
some_string.gsub(/.{66}/, "\n")
If you're interested in exploring an answer that doesn't use RegEx, try something like:
a = "Your string goes here"
d = 66
Array(0..a.length/d).collect {|j| a[j*d..(j+1)*d-1]}.join("\n")
The RegEx is likely faster, but this uses the Array Constructor, .collect and .join so it might be an interesting learning exercise. The first part generates an array of numbers based on the number of chunks (a.length/d). The collect gathers the substrings in to an array. The body of the collect generates substrings by ranges on the original string, and the join puts it back together with '\n' separators.
Use the following to split the string into an array of strings of length 66 and join those strings with a newline character.
some_string.scan(/.{1,66}/).join("\n")