What does \d+ mean in a regular expression?
\d is a digit (a character in the range [0-9]), and + means one or more times. Thus, \d+ means match one or more digits.
For example, the string "42" is matched by the pattern \d+.
You can also find explanations for pieces of regular expressions like this using a tool like Regex101 (online, free) or Regex Coach (downloadable for Windows, free) that will let you enter a regular expression and sample text, then indicate what (if anything) matches the regex. They also try to explain, in words, what the regular expression does.
\d is called a character class and will match digits. It is equal to [0-9].
+ matches 1 or more occurrences of the character before.
So \d+ means match 1 or more digits.
\d means 'digit'. + means, '1 or more times'. So \d+ means one or more digit. It will match 12 and 1.
\d is a digit, + is 1 or more, so a sequence of 1 or more digits
Related
Why is the regular expression ([£€$¥£]|USD|US\$)\s?(\d*.?\d+|\d{1,3}(,\d{3})*(.\d+)?) not matching US$ 150,000.00
Regular expression 1 :
([£€$¥£]|USD|US\$)\s?
matches US$
Regular expression 2 :
(\d*\.?\d+|\d{1,3}(,\d{3})*(\.\d+)?)
matches 150,000.00
Concatenation of two expressions
([£€$¥£]|USD|US\$)\s?(\d*\.?\d+|\d{1,3}(,\d{3})*(\.\d+)?)
does not match US$ 150,000.00
demo : https://regex101.com/r/fJJWqv/1
EDIT : The Regular expression 2 does not match 150,000.00 but shouldn't it match the comma too because of (,\d{3})* ?
Your second claim is untrue. (\d*\.?\d+|\d{1,3}(,\d{3})*(\.\d+)?) does not match 150,000.00. Rather, it matches 150 and 000.00. Since only the former is prefixed with US $, only it matches the third regex.
The reason for this is that the alternation order you specified favors a shorter match. To fix it, you can switch the alternation order: change (\d*\.?\d+|\d{1,3}(,\d{3})*(\.\d+)?) to (\d{1,3}(,\d{3})*(\.\d+)?|\d*\.?\d+).
In 150,000.00 using pattern (\d*\.?\d+|\d{1,3}(,\d{3})*(\.\d+)?) it will not match the comma because the 150 will be matched by \d*\.?\d+ and none of the alternatives start with a comma.
It can because \d* means 0+ digits so that will match 150. Then the \.? is an optional dot so it continues to \d+.
Due to bracktracking the \d* can give up one match to match at least 1 digit from \d+ and 150 will stay the match.
Then the next character is a , but non of the alternations start with a comma so the next character is tried and this time this pattern \d*\.?\d+ can match the 000.00.
One option to match your value (and if you only want the match you can omit the capturing groups) is you remove this part \d*\.?\d+
(?:[£€$¥£]|USD|US\$)\s?\d{1,3}(?:,\d{3})*(?:\.\d+)?
Regex demo
I want to match a pattern with regex, the pattern is:
A-Za-z1-9[0-9-0-9]
so for example:
test1[1-50]
Can you help me ?
Solution update:
^[A-Za-z0-9]+\[[0-9]+-[0-9]+]$
Use this regex: [A-Za-z]+[1-9]\[[0-9]+-[0-9]+\]. You might also want to add \b at the start of the regex to match only after non words character.
[A-Za-z]+ matches things like test, only letters are accepted, one or more times
[1-9] matches a any digit but 0
\[[0-9]+-[0-9]+\] matches one or more digits twice and separated with -. All this must be enclosed with square brackets. (You need to escape those with \ because they are metacharacters)
I noticed some interesting behaviour with some regex work I am doing, and I'd like some insight.
From what I understand, the word character, \w should match the following [a-zA-Z_0-9]
Given this input,
0000000060399301+0000000042456971+0000000
What should this regex
(\d+)\w
Capture?
I would expect it to capture 0000000060399301 but it actually captures 000000006039930
Is there something I am missing? Why is the 1 dropped from the end?
I noticed if I changed the regex to
(\d+\w)
It captures correctly i.e. including the 1
Anyone care to explain? Thanks
You require the regex to match a trailing word character - that would be the 1.
It cannot be another character, because
+ is not a word class character
+ is not a digit
matching is greedy
\d+ - matches one or more digit characters.
\w+ - matches one or more word characters. [A-Za-z\d_]
So with this string 0000000060399301+, \d+ in this (\d+)\w regex matches all the digits (including the 1 before +) at very first, since the following pattern is \w , regex engine tries to find a match, so it backtracks one character to the left and forces \w to match the digit before + . Now the captured group contains 000000006039930 and the last 1 is matched by \w
The 1 is being dropped because \w isn't in the capture group.
I'd like to find a string in url with notepad++ regular expression. Unfortunately I can't.
http://www.example.com/profile/mera-handelsgesellschaft-mbh-182055?category_id=154331
What I want to have is 182055
I will only find it. Not change.
My last try was ([^\-|^\=])(\d+)([^\?])
How can I find it
try this regex please:
\d+(?=\?)
\d look for a digits
\d+ look for one or more digits
(?=\?) is a Positive Lookahead. This means that select one or more digits that there is a ? character after them.
from regex101:
\d+ match a digit [0-9]
Quantifier: + Between one and unlimited times, as many times as possible, giving back as needed [greedy]
(?=\?) Positive Lookahead - Assert that the regex below can be matched
\? matches the character ? literally
Regex101 Demo
I am using regular expression to validate a pattern followed by a fraction. I found these and they match what I need. Overall I want to match 1 to 2 numbers followed by the fraction. How are these expressions different?
/^[0-9]+(?:[\xbc\xbd\xbe])$/ugm
/^\d+(?:[\xbc\xbd\xbe])$/ugm
/^\w+(?:\w+)$/ugm
I need to match the following:
12½
1¼
11¾
but not match..
111½
11111¼
0¾
Well to begin with, [0-9] matches any character of: (0 to 9) and is not the same as \d
\d matches digits (0-9) and other digit characters such as Unicode.
\w matches any word character (letter, number, or underscore)
Although these given expressions may match the same pattern, you will eventually fail using your 3rd solution.
It will match a pattern like foobar where as you can see there are no (0-9) characters or Unicode fractions in this pattern.
And with running a quick benchmark, your 2nd solution is about 16% slower than your first, plus it matches Unicode and other digit characters.
I would stick with your first expression, and change it to match between 1-2 number characters.
/^[1-9][0-9]?(?:[\xbc\xbd\xbe])$/ugm
or even
/^[1-9][0-9]?(?:[\xbc-\xbe])$/ugm
Try the following:
^[1-9][0-9]?[\xbc\xbd\xbe]$
[0-9] and \d are equivalent. \w matches a "word" character. The expression [1-9] matches a digit which is not zero (since you specifically asked how to exclude that).
This unattractively hard-codes for some legacy 8-bit character set; for future compatibility, you should consider switching to Unicode.
You can try
/^[1-9][0-9]?(?:[\xbc\xbd\xbe])$/ugm