Could somebody help me with regex? Basically, I would like a regex which matches with decimal numbers.
Allowed types:
12
1.3234
0.3423434
23423.12
Not allowed types:
0012
12.324.12
01.2332
.12
121212.
Thanks for your help in advance!
Regards!
This regex should do your job.
^(?:[1-9][0-9]*|0)(?:\.[0-9]+)?$
^ - Start of string(?: - Beginning of a non-capture group[1-9][0-9]* - Matches a number not starting with a zero|0 - Or allows matching only a zero to allow numbers like 0.3423434 or 0.1(?:\.[0-9]+)? - Optionally allows a decimal part in the number$ - End of stringEdit: Based on Allan's suggestion to use \d instead of [0-9]
In case your input only contains English numbers, or when you only intend to match English numbers, then using [0-9] should be preferred for reasons like better performance and wide supported of it across regex engines.
But in case your input contains digits from other languages like Hindi १ २ etc. and you want to match any digits, then \d should be preferred instead of [0-9]
^(?:[1-9]\d*|0)(?:\.\d+)?$ is even better if \d is recognized in OP language
\d should be used if one is intending to also match Unicode digits in languages other than English like Hindi १ or ४. But instead of one only expects to match only English numbers 0 to 9 then using [0-9] give relatively better performance as then it just checks for 0 to 9 English number literals only. So up to OP based upon his input. And thanks again for suggestion, which allowed me to clarify the reason of using [0-9]. Let me update that in my post to make it clear.
That would be
^[[:digit:]]+(\.[[:digit:]]+)?$
Beginning of the string, then one or more digits, then (optionally) a dot and one or more digits, then the end of the string.
If you want to cater for the sign, add [+-]? after the ^.
0012 and 01.2332... It shouldn't... You need to add constraint on the first digit encounteredYou could use an alternation
^(?:0\.\d*[1-9]\d*|[1-9]\d*(?:\.\d+)?)$
Explanation
^ Start of string(?: Non capturing group
0\. Match a single zero followed by a dot\d*[1-9]\d* Match 0+ digits, a digit 1-9 and again 0+ digits t prevent only zeroes to match| Or[1-9]\d* Match a digit 1-9 followed by 0+ digits(?:\.\d+)?) Optional part to match a dot and 1+ digits) Close non capturing group
^(?:0\.\d*[1-9]\d*|[1-9]\d*(?:\.\d+)?)$demo