I have tried
^[a-zA-Z0-9]*[a-zA-Z][a-zA-Z0-9]*$
&
^(?![0-9]*$)[a-zA-Z0-9]+$
but both are allowing numbers only as well.
You may try this:
^(?=.*[a-zA-Z])[a-zA-Z0-9]+$
Explanation:
^ start of string.
(?=.*[a-zA-Z]) positive look ahead, that ensures there exists
one or more a-zA-Z; if true then :
[a-zA-Z0-9]+ this matches one or more combination of alphanumeric characters.
$ end of string.
Demo
Related
I would like to have an expression to validate the plates of monaco.
They are written as follows:
A123
123A
1234
I started by doing:
^[a-zA-Z0-9]{1}?[0-9]{2}?[a-zA-Z0-9]{1}$
But the case A12A which is false is possible with that.
You can use
^(?!(?:\d*[a-zA-Z]){2})[a-zA-Z\d]{4}$
See the regex demo. Details:
^ - start of string
(?!(?:\d*[a-zA-Z]){2}) - a negative lookahead that fails the match if there are two occurrences of any zero or more digits followed with two ASCII letters immediately to the right of the current location
[a-zA-Z\d]{4} - four alphanumeric chars
$ - end of string.
You can write the pattern using 3 alternatives specifying all the allowed variations for the example data:
^(?:[a-zA-Z][0-9]{3}|[0-9]{3}[a-zA-Z]|[0-9]{4})$
See a regex demo.
Note that you can omit {1} and
To not match 2 chars A-Z you can write the alternation as:
^(?:[a-zA-Z]\d{3}|\d{3}[a-zA-Z\d]|\d[a-zA-Z\d][a-zA-Z\d]\d)$
See another regex demo.
So it needs 3 connected digits and 1 letter or digit.
Then you can use this pattern :
^(?=.?[0-9]{3})[A-Za-z0-9]{4}$
The lookahead (?=.?[0-9]{3}) asserts the 3 connected digits.
Test on Regex101 here
I'd like to use Regex to determine whether the characters after the first are all numbers.
For example:
A123 would be valid as after A there are only numbers
A12B would be invalid as, after the first character, there is another letter
I essentially want to ignore the first character
I have so far this:
(?<=A)\w*(?=)
but this makes A12B or A1B2C valid, I only want numbers after A.
You could match not a digit \D, followed by matching 1+ times a digit. If that is the whole string, you could use anchors asserting the start ^ and the $ end of the string.
^\D\d+$
That will match:
^ Start of the string
\D Match not a digit
\d+ Match 1+ digits making sure there are digits
$ End of the string
Regex demo
The best solution I can think of is:
^.\d*$
^ - Start of the line
. - Any character (except line terminators)
\d*
\d- a number
* - repeated any number of times (including 0 times. If you want it to be at least 1, change it to +).
$ - End of the line
let regex = /^.\d*$/;
let testStrings = ['A123', 'A12B'];
testStrings.forEach(str => {
console.log(`${str} is ${regex.test(str) ? 'valid' : 'invalid'}`);
});
Your attempt is very complicated, especially given how simple is your goal.
Succeeding at regexes is all about simplicity.
The first character can be anything, so just go with ..
The next ones are all digits, so you want \d.
You'll star it to specify restriction-less repetition, or use + if you want at least one.
Finally, you need to anchor your regex at the beginning and at the end, else it would match stuff like A123XXXXX or XXXXA123.
Note that most implementations of match will already anchor the pattern at the end, so you can omit the caret at the beginning.
Final regex:
^.\d*$
Maybe
(?<=.{1,1})([0-9]+)(?=\s)
(?<=.{1,1}) - has exactly one character before
([0-9]+) - at least one digit
(?=\s) - has a whitespace after
Add ^ at the beginning - to specify beginning of line
Replace (?=\s) with $ for end of line
^[a-zA-Z][0-9]{3}$
^ - "starting with" (Here it is starting with any letter). Read it as ^[a-zA-Z]
[a-z] - any small letters and A-Z any capital letters (you may change if required.)
[0-9] - any numbers
{3} - describes how many numbers you want to check. You have to read it as [0-9]{3}
$ - End of the statement. (Means, in this case it will end up with 3 numbers)
Here you can play around - https://regex101.com/r/mqUHvP/5
I the below items i want to only detect the valid items with regular expression.
Space in word means invalid, # sign means invalid, Starting word with number is invalid.
Invalid : M_123 ASD
Invalid : M_123#ASD
Invalid : 1_M# ADD
Valid : M_125ASD
Valid : M_125$ASD
I am trying as below :
[A-Za-z0-9_$]
Not working properly. I need to set both valid and invalid sets for a word.
Can i do a match with regular expression?
Your regex [A-Za-z0-9_$] presents a character class that matches a single character that is either an ASCII letter or digit, or _ or $ symbols. If you use it with std::regex_match, it would only match a whole string that consists of just one char like that since the pattern is anchored by default when used with that method. If you use it with an std::regex_search, a string like ([_]) would pass, since the regex is not anchored and can find partial matches.
To match 0 or more chars, you need to add * quantifier after your class. To match one or more chars, you need to add + quantifier after your character class. However, you have an additional restriction: a digit cannot appear at the start.
It seems you may use
^[A-Za-z][A-Za-z0-9_$]*$
See the regex demo at regex101.com.
Details:
^ - start of string
[A-Za-z] - an ASCII letter (exactly one occurrence)
[A-Za-z0-9_$]* - 0+ ASCII letters, digits, _ or $
$ - end of string anchor.
Note that with regex_match, you may omit ^ and $ anchors.
So the requirements are
cannot start with number( i am assuming it as start with alphabet)
cannot contain space or #
all other characters are valid
you can try this regex ^[a-zA-Z]((?![\# ]).)+?$
^[a-zA-Z] checks for alphabet at start of the line
((?![\# ]).)+?$ checks if there are no # or space in the remaining part of the line.
Online demo here
EDIT
As per Wiktor's comment the regex can be simplified to ^[a-zA-Z][^# ]+$.
I have written a regular expression as follows:
"^[\+]{0,1}([\#]|[\*]|[\d]){1,15}$"
In summary this matches an optional '+' sign followed by up to 15 characters which might be '#', '*' or a digit.
However, this means that '+#' will match and this is not a valid result as I always need at least one number.
Typical valid matches might be:
+1234
445678999
+#7897897
+345764756#775
So, given that I've crafted a valid RegEx for these to match, I guess the elegant solution is to use this regex and add some special criterion to globally check for a digit in the result OR somehow disallow anything which doesn't have at least one digit in.
How do I check for that digit?
This solutions requires at least one digit in the string, using lookahead (the (?=...) section):
^(?=.*\d)\+?[#*\d]{1,15}$
Legenda
^ # Start of the string (or line with m/multiline flag)
(?=.*\d) # Lookahead that checks for at least one digit in the match
\+? # An optional literal plus '+'
[#*\d]{1,15} # one to fifteen of literal '#' or '*' or digit (\d is [0-9])
$ # End of the string (line with m/multiline flag)
Online Demo
Regex graphical schema (everybody loves it)
NOTE: as you can see in the demo avoid also combinations just like +* or + or #* , you get it...
Try this regex (my first idea initially):
^(?=.*[0-9])[+]?([#*\d]{1,15})$
You can replace [0-9] with \d.
DEMO:
https://regex101.com/r/bM9oE6/3
I'd use
^(?=.*\d)\+?[#*\d]{1,15}$
Explanation:
^ : begining of line
(?= : lookahead
.*\d : at least one digit
)
\+? : optional +
[#*\d]{1,15} : 1 to 15 character in class [#*\d]
$ : end of line
matched:
+1234
445678999
+#7897897
+345764756#775
###456
not matched:
+#*
+*
#*
+#
This should work in your case:
^(\+{0,1}[\d#]{1,15})$
Demo:
https://regex101.com/r/fU1eC2/1
Edit:
If you need # after + in string use ^[+#]?([\d#]{1,15})(?<!#)$
matches "+#7897897"
If don't, use ^[+#]*([\d#]{1,15})(?<!#)$
matches "+#7897897"
It is for a normal register name, could be 1-n characters with a-zA-Z and -, like
larry-cai, larrycai, larry-c-cai, l,
but - can't be the first and end character, like
-larry, larry-
my thinking is like
^[a-zA-Z]+[a-zA-Z-]*[a-zA-Z]+$
but the length should be 2 if my regex
should be simple, but don't how to do it
Will be nice if you can write it and pass http://tools.netshiftmedia.com/regexlibrary/
You didn't specify which regex engine you're using. One way would be (if your engine supports lookaround):
^(?!-)[A-Za-z-]+(?<!-)$
Explanation:
^ # Start of string
(?!-) # Assert that the first character isn't a dash
[A-Za-z-]+ # Match one or more "allowed" characters
(?<!-) # Assert that the previous character isn't a dash...
$ # ...at the end of the string.
If lookbehind is not available (for example in JavaScript):
^(?!-)[A-Za-z-]*[A-Za-z]$
Explanation:
^ # Start of string
(?!-) # Assert that the first character isn't a dash
[A-Za-z-]* # Match zero or more "allowed" characters
[A-Za-z] # Match exactly one "allowed" character except dash
$ # End of string
This should do it:
^[a-zA-Z]+(-[a-zA-Z]+)*$
With this there need to be one or more alphabetic characters at the begin (^[a-zA-Z]+). And if there is a - following, it needs to be followed by at least one alphabetic character (-[a-zA-Z]+). That pattern can be repeated arbitrary times until the end of the string is reached.
A simple answer would be:
^(([a-zA-Z])|([a-zA-Z][a-zA-Z-]*[a-zA-Z]))$
This matches either a string with length 1 and characters a-zA-Z or it matches an improved version of your original expression which is fine for strings with length greater than 1.
Credit for the improvement goes to Tim and ridgerunner (see comments).
Try this:
^[a-zA-Z]+([-]*[a-zA-Z])*$
Not sure which lazy group takes precedence..
^[a-zA-Z][a-zA-Z-]*?[a-zA-Z]?$
maybe this?
^[^-]\S*[^-]$|^[^-]{1}$