Creating a regex to match numbers or a range of number

Question

I've been looking at regex help pages but cant seem to find/understand a solution.

My problem is: I want a regex that allows either specifically a number or a range of numbers that will be integrated in a code for data input validation. For example one can only input either "12" or "12-50" with that exact same format, no extra dashes or anything.

The solution I created for the ex."12-50" is [0-9][-][0-9] and works perfectly fine. However I can't integrate the above regex with one that will allow that format and also the format of just a single number.

I tried using the OR operator, [0-9]|[0-9][-][0-9], however it doesn't seem to work perfectly as I can input "incorrect formats" such as "12-","123---" etc.

Have the dash and the two following digits be an optional group? `/\d\d(-\d\d)?/` — CertainPerformance, Jul 12 '18 at 07:12
Possible duplicate of [Match whole string](https://stackoverflow.com/questions/6298566/match-whole-string) — melpomene, Jul 12 '18 at 07:15
Tried ^[0-9]$|^[0-9][-][0-9]$ however its not working. I'm sorry but I'm new at using regex. — Carl Carl, Jul 12 '18 at 07:19

score 0 · Accepted Answer · answered Jul 12 '18 at 07:20

Firstly [0-9][-][0-9] is not matching the whole of "12-50", just the "2-5" substring. And that explains your false positives: in each case the regex is matching a substring.

Therefore you need to start by matching the whole string: ^…$.

Also, you want sequences of digits rather than single digits so say that: \d+ matches one or more digits ('\d' matches a digit^[1]).

So something like:

^\d+(-\d+)?$

should work. Expanding this

^         Start of string
\d+       One or more digits
(         Start of group
   -\d+   Dash followed by one or more digits
)         End of group
?         Preceding element – the group – is optional
$         End of string

^[1] it, depending on your specific regex engine, may match non-ASCII digits from Unicode, but you'll need to check your documentation for that.

score 0 · Answer 2 · answered Jul 12 '18 at 07:24

0

As you want exact match pattern, you need to use start and ending indicator.

^ : Indicate starting

$ : Indicate ending

| : To give more than one regex using or condition

'+' : To find atleast one accurance

^(([0-9]+)|([0-9]+[-][0-9]+))$

answered Jul 12 '18 at 07:24

Bhavesh

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Creating a regex to match numbers or a range of number

2 Answers2