I have to check if a 4 character string is all valid hex, I found another question which demonstrates exactly what I want to do but it's Java: Regex to check string contains only Hex characters
How can I accomplish this?
I read the ruby docs for Regular expressions, but I don't understand how to return a true or false based on this match?
In ruby regex \h matches a hex digit and \H matches a non-hex digit.
So
!str[/\H/] is what you're looking for.
if str =~ /^[0-9A-F]+$/
does the trick. If you want case insensitive then:
str =~ /^[0-9A-F]+$/i
pattern = /^[[:xdigit:]]+$/
And then just check:
if pattern === your_string
if /^[[:xdigit:]]+$/ === your_string
or with
if your_string.match?(/^[[:xdigit:]]+$/)
Related
Using a regex, how can I match strings that end with exactly one . as:
This is a string.
but not those that end with more than one . as:
This is a string...
I have a regex that detects a single .:
/[\.]{1}\z/
but I do not want it to match strings that end in ....
What you want is a 'negative lookbehind' assertion:
(?<!\.)\.\z
This looks for a period at the end of a string that isn't preceded by a period. The other answers won't match the following string: "."
Also, you may need to look out for unicode ellipsis characters…
You can detect this like so: str =~ /\u{2026}/
You can use:
[^\.][\.]\z
You are looking for a string that before the last dot there is a char that is not a dot.
I like Regexr a lot!
Solution similar to Dekel:
[^.]+[.]
Live demo
I need the username to be two or more characters of a-z, 0-9, all downcase. This is the current regex I am using
USER_REGEX = /\A[a-z0-9][-a-z0-9]{1,19}\z/i
With this regex, users are able to use uppercase charters in their username. How do I modify the current regex to avoid that?
The regular expression to filter for two to twenty lower-case characters or digits is
/^[a-z0-9]{2,20}$/
which means:
^ at the front of input
a-z accept lower-case 'a' through 'z'
0-9 accept '0' through '9'
{2,20} accept 2 to 20 elements from preceding [] block
$ until the end of input
You can make a regular expression case-insensitive with trailing i, as in your example; that appears to be the root of problem. That said, I don't know Ruby's peculiarities with respect to regular expressions.
If you must keep the RegEx - remove the "i" from the end
USER_REGEX = /\A[a-z0-9][-a-z0-9]{1,19}\z/i
USER_REGEX = /\A[a-z0-9][-a-z0-9]{1,19}\z/
the "i" tells the RegEx to be a case-insensitive RegEx.
but you want it to be case-sensitive and only match on lowercase letters.
Need parse a lot of text files and replace any quoted strings containing cyrillic symbols. They are may contains new lines, non-alphabetic characters and special symbols (for example '$' or escaped quote).
Can anyone help with regex?
From comments:
for example php code
function hello($word) {
$word2 = "ха-ха!";
echo "Привет, $word $word2\n";
}
hello('Мир');
I need match "ха-ха!", "Привет, $word $word2\n" and 'Мир'
This should work:
str = 'The cat is under the "таблица"'
regex = /"\p{Cyrillic}+.*?\.?"/ui
str.match(regex){|s| do_stuff_with_each_matching s}
# or...
str.gsub!(regex){|s| method_that_translates_russian s}
Check it out on live at http://rubular.com/r/0Mwbfinjvp.
http://www.ruby-doc.org/core-1.9.3/Regexp.html
".*[^a-zA-Z\d]+.*" matches any quoted character sequence containing at least one non-alphanumeric character.
i.e. it matches "aa$bb" and "a1$b1"
It doesn't match "aabb" or a$b.
Hope that this is what you want (Add required escaping).
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 want to remove any leading and trailing non-alphabetic character in my string.
for eg. ":----- pt-br:-" , i want "pt-br"
Thanks
result = subject.gsub(/\A[\d_\W]+|[\d_\W]+\Z/, '')
will remove non-letters from the start and end of the string.
\A and \Z anchor the regex at the start/end of the string (^/$ would also match after/before a newline which is probably not what you want - but that might not matter in this case);
[\d_\W]+ matches one or more digits, the underscore or anything else that is not an alphanumeric character, leaving only letters.
| is the alternation operator.
In ruby 1.9.1 :
":----- pt-br:-".partition( /[a-zA-Z](...)[a-zA-Z]/ )[1]
partition searches the pattern in the string and returns the part before it, the match, and the part after it.
result = subject.gsub(/^[^a-zA-Z]+/, '').gsub(/[^a-zA-Z]+$/, '')