i have a string like
/root/children[2]/header[1]/something/some[4]/table/tr[1]/links/a/b
and
/root/children[2]/header[1]/something/some[4]/table/tr[2]
how can i reproduce the string so that all the /\[\d+\]/ are removed except for the last /\[\d+\]/ ?
so i should end up with .
/root/children/header/something/some/table/tr[1]/links/a/b
and
/root/children/header/something/some/table/tr[2]
No loops for you. Use a lookahead assertion (?= ... ):
s.gsub(/\[\d+\](?=.*\[)/, "")
There's a reasonable explanation of the very useful lookaround operators here
We will have to use while loop, I guess. And here comes good ol' C-style-loop solution:
while s.gsub!(/(\[\d+\])(.*?)(\[\d+\])/, '\2\3'); end
It's a bit hard to read, so I'll explain. The idea is that we match the string with a pattern that requires two [\d+] blocks to persist in a string. In the replacement, we just delete the first one. We repeat it until string doesn't match (so it contains only one such block) and utilize the fact that gsub! doesn't perform substitution when string is unmatched.
I'm absolutely certain there's a more elegant solution, but this ought to get you going:
string = "/root/children[2]/header[1]/something/some[4]/table/tr[1]/links/a/b"
count = string.scan(/\[\d+\]/).size
index = 0
string.gsub(/\[\d+\]/) do |capture|
index += 1
index == count ? capture : ""
end
Try this:
str.scan(/\[\d+\]/)[0..-2].each {|match| str.sub!(match, '')}
Related
Original string '4.0.0-4.0-M-672092'
How to modify the Original string to "4.0-M-672092" using a one line code.
Any Help is highly appreciated .
Thanks and Regards
The 'split' method works in this case
https://apidock.com/ruby/String/split
'4.0.0-4.0-M-672092'.split('-')[1..-1].join('-')
# => "4.0-M-672092"
Just be careful, in this application is fine, but in long texts this might become unoptimized, since it splits all the string and then joins the array all over again
If you need this in wider texts to be more optimized, you can find the "-" index (which is your split) and use the next position to make a substring
text = '4.0.0-4.0-M-672092'
text[(text.index('-') + 1)..-1]
# => "4.0-M-672092"
But you can't do it in one line, and not finding a split character will result in an error, so use a rescue statement if that is possible to happen
Simplest way:
'4.0.0-4.0-M-672092'.split('-', 2).second
"4.0.0-4.0-M-672092"[/(?<=-).*/]
#=> "4.0-M-672092"
The regular expression reads, "Match zero or more characters other than newlines, as many as possible (.*), provided the match is preceded by a hyphen. (?<=-) is a positive lookbehind. See String#[].
I'm trying to write a regex to validate a string and accepts only a series of four comma-separated digits, each up to 100. Something like this would be valid:
20,30,40,50
and these invalid:
120,0,20,0
20,30,40,ss
invalid_string
Any thoughts?
They're used for CMYK colours. We just need to store them here, not use them.
Number Range and Subroutine
In Ruby 2+, for a compact regex, use this:
^([0-9]|[1-9][0-9]|100)(?:,\g<1>){3}$
Explanation
The ^ anchor asserts that we are at the beginning of the string
The parentheses around ([0-9]|[1-9][0-9]|100) match a number from 0 to 100 and define subroutine #1
(?:,\g<1>) matches one comma and the expression defined by subroutine # 1
The {3} quantifier repeats that three times
The $ anchor asserts that we are at the end of the string
I'd save myself the headache of using regex for a number related problem. Also the validation message will look akward so it's better to make your own:
validate :that_string_has_only_4_numbers_upto_100
def that_string_has_only_4_numbers_upto_100
errors.add(:str, 'is not valid.') unless str.split(/,/).all? { |n| 1..100 === n.to_i }
end
Unless you a re regex jedi guru like #zx81 :p.
^(?:\d{1,2},){3}\d{1,2}$
Try this
In Ruby, what regex will strip out all but a desired string if present in the containing string? I know about /[^abc]/ for characters, but what about strings?
Say I have the string "group=4&type_ids[]=2&type_ids[]=7&saved=1" and want to retain the pattern group=\d, if it is present in the string using only a regex?
Currently, I am splitting on & and then doing a select with matching condition =~ /group=\d/ on the resulting enumerable collection. It works fine, but I'd like to know the regex to do this more directly.
Simply:
part = str[/group=\d+/]
If you want only the numbers, then:
group_str = str[/group=(\d+)/,1]
If you want only the numbers as an integer, then:
group_num = str[/group=(\d+)/,1].to_i
Warning: String#[] will return nil if no match occurs, and blindly calling nil.to_i always returns 0.
You can try:
$str =~ s/.*(group=\d+).*/\1/;
Typically I wouldn't really worry too much about a complex regex. Simply break the string down into smaller parts and it becomes easier:
asdf = "group=4&type_ids[]=2&type_ids[]=7&saved=1"
asdf.split('&').select{ |q| q['group'] } # => ["group=4"]
Otherwise, you can use regex a bunch of different ways. Here's two ways I tend to use:
asdf.scan(/group=\d+/) # => ["group=4"]
asdf[/(group=\d+)/, 1] # => "group=4"
Try:
str.match(/group=\d+/)[0]
I have a string in Ruby:
str = "<TAG1>Text 1<TAG1>Text 2"
I want to use gsub to get a string like this:
want = "<TAG2>Text 1</TAG2><TAG2>Text2</TAG2>"
In other words, I want to save everything in between a <TAG1> and EITHER: 1) the next occurrence of a "<", or 2) the end of the string.
The best regex i could come up with was:
regex = /<TAG1>(.*)(?:<|$)/
But the problem with this is that it'll just match the entire str, where what I want is both matches within str. (In other words, it seems like the end of string char ($) seems to have precedence over the "<" character--is there a way to flip it around?
/<TAG1>([^<]*)/ will match that. If there's no < it'll go all the way to the end of the string. Otherwise it will stop when it hits a <. Your problem is that . matches < as well. An alternative way would be to do /<TAG1>(.*?)(?:<|$)/, which makes the * non-greedy.
Ruby 1.9.1, OSX 10.5.8
I'm trying to write a simple app that parses through of bunch of java based html template files to replace a period (.) with an underscore if it's contained within a specific tag. I use ruby all the time for these types of utility apps, and thought it would be no problem to whip up something using ruby's regex support. So, I create a Regexp.new... object, open a file, read it in line by line, then match each line against the pattern, if I get a match, I create a new string using replaceString = currentMatch.gsub(/./, '_'), then create another replacement as whole string by newReplaceRegex = Regexp.escape(currentMatch) and finally replace back into the current line with line.gsub(newReplaceRegex, replaceString) Code below, of course, but first...
The problem I'm having is that when accessing the indexes within the returned MatchData object, I'm getting the first result twice, and it's missing the second sub string it should otherwise be finding. More strange, is that when testing this same pattern and same test text using rubular.com, it works as expected. See results here
My pattern:
(<(?:WEBOBJECT|webobject) (?:NAME|name)=(?:[a-zA-Z0-9]+.)+(?:[a-zA-Z0-9]+)(?:>))
Text text:
<WEBOBJECT NAME=admin.normalMode.someOtherPatternWeDontWant.moreThatWeDontWant>moreNonMatchingText<WEBOBJECT NAME=admin.SecondLineMatch>AndEvenMoreNonMatchingText
Here's the relevant code:
tagRegex = Regexp.new('(<(?:WEBOBJECT|webobject) (?:NAME|name)=(?:[a-zA-Z0-9]+\.)+(?:[a-zA-Z0-9]+)(?:>))+')
testFile = File.open('RegexTestingCompFix.txt', "r+")
lineCount=0
testFile.each{|htmlLine|
lineCount += 1
puts ("Current line: #{htmlLine} at line num: #{lineCount}")
tagMatch = tagRegex.match(htmlLine)
if(tagMatch)
matchesArray = tagMatch.to_a
firstMatch = matchesArray[0]
secondMatch = matchesArray[1]
puts "First match: #{firstMatch} and second match #{secondMatch}"
tagMatch.captures.each {|lineMatchCapture|
puts "Current capture for tagMatches: #{lineMatchCapture} of total match count #{matchesArray.size}"
#create a new regex using the match results; make sure to use auto escape method
originalPatternString = Regexp.escape(lineMatchCapture)
replacementRegex = Regexp.new(originalPatternString)
#replace any periods with underscores in a copy of lineMatchCapture
periodToUnderscoreCorrection = lineMatchCapture.gsub(/\./, '_')
#replace original match with underscore replaced copy within line
htmlLine.gsub!(replacementRegex, periodToUnderscoreCorrection)
puts "The modified htmlLine is now: #{htmlLine}"
}
end
}
I would think that I should get the first tag in matchData[0] then the second tag in matchData1, or, what I'm really doing because I don't know how many matches I'll get within any given line is matchData.to_a.each. And in this case, matchData has two captures, but they're both the first tag match
which is: <WEBOBJECT NAME=admin.normalMode.someOtherPatternWeDontWant.moreThatWeDontWant>
So, what the heck am I doing wrong, why does rubular test give me the expected results?
You want to use the on String#scan instead of the Regexp#match:
tag_regex = /<(?:WEBOBJECT|webobject) (?:NAME|name)=(?:[a-zA-Z0-9]+\.)+(?:[a-zA-Z0-9]+)(?:>)/
lines = "<WEBOBJECT NAME=admin.normalMode.someOtherPatternWeDontWant.moreThatWeDontWant>moreNonMatchingText\
<WEBOBJECT NAME=admin.SecondLineMatch>AndEvenMoreNonMatchingText"
lines.scan(tag_regex)
# => ["<WEBOBJECT NAME=admin.normalMode.someOtherPatternWeDontWant.moreThatWeDontWant>", "<WEBOBJECT NAME=admin.SecondLineMatch>"]
A few recommendations for next ruby questions:
newlines and spaces are your friends, you don't loose points for using more lines on your code ;-)
use do-end on blocks instead of {}, improves readability a lot
declare variables in snake case (hello_world) instead of camel case (helloWorld)
Hope this helps
I ended up using the String.scan approach, the only tricky point there was figuring out that this returns an array of arrays, not a MatchData object, so there was some initial confusion on my part, mostly due to my ruby green-ness, but it's working as expected now. Also, I trimmed the regex per Trevoke's suggestion. But snake case? Never...;-) Anyway, here goes:
tagRegex = /(<(?:webobject) (?:name)=(?:\w+\.)+(?:\w+)(?:>))/i
testFile = File.open('RegexTestingCompFix.txt', "r+")
lineCount=0
testFile.each do |htmlLine|
lineCount += 1
puts ("Current line: #{htmlLine} at line num: #{lineCount}")
oldMatches = htmlLine.scan(tagRegex) #oldMatches thusly named due to not explicitly using Regexp or MatchData, as in "the old way..."
if(oldMatches.size > 0)
oldMatches.each_index do |index|
arrayMatch = oldMatches[index]
aMatch = arrayMatch[0]
#create a new regex using the match results; make sure to use auto escape method
replacementRegex = Regexp.new(Regexp.escape(aMatch))
#replace any periods with underscores in a copy of lineMatchCapture
periodToUnderscoreCorrection = aMatch.gsub(/\./, '_')
#replace original match with underscore replaced copy within line, matching against the new escaped literal regex
htmlLine.gsub!(replacementRegex, periodToUnderscoreCorrection)
puts "The modified htmlLine is now: #{htmlLine}"
end # I kind of still prefer the brackets...;-)
end
end
Now, why does MatchData work the way it does? It seems like it's behavior is a bug really, and certainly not very useful in general if you can't get it provide a simple means of accessing all the matches. Just my $.02
Small bits:
This regexp helps you get "normalMode" .. But not "secondLineMatch":
<webobject name=\w+\.((?:\w+)).+> (with option 'i', for "case insensitive")
This regexp helps you get "secondLineMatch" ... But not "normalMode":
<webobject name=\w+\.((?:\w+))> (with option 'i', for "case insensitive").
I'm not really good at regexpt but I'll keep toiling at it.. :)
And I don't know if this helps you at all, but here's a way to get both:
<webobject name=admin.(\w+) (with option 'i').