I have a list of words as follows:
cat
concatenate
matter
pattern
hat
rather
fathom
at
saturate
vat
I need a regular expression to match any words which are a single letter followed by the letters 'at'.
I currently have [A-Za-z]at but that includes the 'cat' and 'nat' in 'concatenate' and the 'rat' in 'saturate'.
How can I make it look for exactly one character before, and make sure that there is not more than 1 character before the 'at'. I tried using {1} but that still didn't work. Thanks for your help.
Use word boundary:
\b[A-Za-z]at\b
or, if you have string contains just those 3 characters, then you can use anchors:
^[A-Za-z]at$
You can use ^[A-Za-z]at$
[A-za-z] would check for a single letter. Following at would look for exact match.
Using the ^ and $ sign would force the word to start and end in the given boundaries.
Related
I really don't use RegEx that much. You could say I am RegEx n00b. I have been working on this issue for a half a day.
I am trying to write a pattern that looks backward from a number character. For example:
1. bob1 => bob
2. cat3 => cat
3. Mary34 => Mary
So far I have this (?![A-Z][a-z]{1,})([A-Za-z_])
It only matches for individual characters, I want all the characters before the number character. I tried to add the ^ and $ into my pattern and using an online simulator. I am unsure where to put the ^ and $.
NOTE: I am using RegEx for the .NET Framework
You may use a regex like
[\p{L}_]+(?=\d)
or
[\w-[\d]]+(?=\d)
See the regex demo
Pattern details
[\p{L}_]+ - any 1 or more letters (both lower- and uppercase) and/or _
OR
[\w-[\d]]+ - 1 or more word chars except digits (the -[] inside a character class is a character class subtraction construct)
(?=\d) - a positive lookahead that requires a digit to appear immediately to the right of the current location
If we break down your RegEx, we see:
(?![A-Z][a-z]{1,}) which says "look ahead to find a string that is NOT one uppercase letter followed one or more lowercase letters" and ([A-Za-z_]) which says "match one letter or underscore". This should end up matching any single lowercase letter.
If I understand what you want to achieve, then you want all of the letters before a number. I would write something like that as:
\b([a-zA-Z]+)[0-9]
This will start at a word boundary \b, match one or more letters, and require a digit right after the matched string.
(The syntax I used seems to match this document about .NET RegEx: https://learn.microsoft.com/en-us/dotnet/standard/base-types/regular-expressions)
In light of Wiktor Stribizew's comment, here is a pure match RegEx:
\b[a-zA-Z_]+(?=[0-9])
This matches the pattern and then looks ahead for the digit. This is better than my first lookahead attempt. (Thank you Wiktor.)
http://www.rexegg.com/regex-lookarounds.html
I am looking to clean up a regular expression which matches 2 or more characters at a time in a sequence. I have made one which works, but I was looking for something shorter, if possible.
Currently, it looks like this for every character that I want to search for:
([A]{2,}|[B]{2,}|[C]{2,}|[D]{2,}|[E]{2,}|...)*
Example input:
AABBBBBBCCCCAAAAAADD
See this question, which I think was asking the same thing you are asking. You want to write a regex that will match 2 or more of the same character. Let's say the characters you are looking for are just capital letters, [A-Z]. You can do this by matching one character in that set and grouping it by putting it in parentheses, then matching that group using the reference \1 and saying you want two or more of that "group" (which is really just the one character that it matched).
([A-Z])\1{1,}
The reason it's {1,} and not {2,} is that the first character was already matched by the set [A-Z].
Not sure I understand your needs but, how about:
[A-E]{2,}
This is the same as yours but shorter.
But if you want multiple occurrences of each letter:
(?:([A-Z])\1+)+
where ([A-Z]) matches one capital letter and store it in group 1
\1 is a backreference that repeats group 1
+ assume that are one or more repetition
Finally it matches strings like the one you've given: AABBBBBBCCCCAAAAAADD
To be sure there're no other characters in the string, you have to anchor the regex:
^(?:([A-Z])\1+)+$
And, if you wnat to match case insensitive:
^(?i)(?:([A-Z])\1+)+$
I'm trying to match the last four characters (alphanumeric) of all words beginning with the sequence &c.
For instance, in the string below, I'd like to match the pieces in bold:
Colour one is &cFF2AC3 and colour two is &c22DE4A.
Can anybody help me with the correct regex expression? I've spent hours on this great resource to no avail.
it looks like hexadecimal numbers, so use this pattern
&c[0-9A-F]{2}\K([0-9A-F]{4})
DEMO
This:
/(?i)\s*&c(?:[a-z0-9]{2})([a-z0-9]{4})\b/
append a g to the end of it if you want it to find all matches in a given text
Try this
/(?:^| )&c\w*(\w{4})\b/
If you want to try it in the regex tester you linked to, make sure to use the g modifier to see all matches.
Explanation: (?:^| ) matches either a space or the start of the string, &c\w* matches the ampersand and the the first however many characters of the word, and then \w{4} captures the last 4 characters. \b on the end asserts a word break (a "non-word" character or the end of the string).
I have three different things
xxx
xxx>xxx
xxx>xxx>xxx
Where xxx can be any combination of letters and number
I need a regex that can match the first two but NOT the third.
To match ASCII letters and digits try the following:
^[a-zA-Z0-9]{3}(>[a-zA-Z0-9]{3})?$
If letters and digits outside of the ASCII character set are required then the following should suffice:
^[^\W_]{3}(>[^\W_]{3})?$
^\w+(?:>\w+)?$
matches an entire string.
\w+(?:>\w+)?\b(?!>)
matches strings like this in a larger substring.
If you want to exclude the underscore from matching, you can use [\p{L]\p{N}] instead (if your regex engine knows Unicode), or [^\W_] if it doesn't, as a substitute for \w.
I need a regular expression to check a string should contain only letters and space.No other character other than letter [A-Z] and space are allowed.
Please help.
The complete regex looks like this
^[A-Z ]+$
You can simply create a character class and put the characters in that you want to allow:
[A-Z ]
if you want to allow also lower case letters then use
[A-Za-z ]
or use the i (IgnoreCase) option
So your character class matches 1 character. you want to repeat it to match more than one character.
+ would be at least one character, where
* would additionally match 0 characters
As last step you need to ensure that the complete string is matched, you can do this using anchors.
^ matches the beginning of the string
$ matches the end of the string (or a newline if you use the m (multiline) option
A character class should be sufficient
[A-Z ]+
i.e. one or more of letters between A-Z and space
Check that the string matches the following:
^[a-zA-Z ]*$
Regex character classes can be negated by putting a ^ symbol at the begining of them.
Your example could be negated like this: [^A-Z]. Add a space to allow the full range of characters you want to check for and you have [^A-Z ].
Now you have a validator that meets your criteria: If that regex returns true then your validation fails.
Since you didn't specify the programming language you're working in, I can't help you much further than that.
This will match what you need:
^[A-Z\s]+$
try matching with this regex
^[A-Za-z\s]+$
this should do the trick