Value pass to regular expression should have specified character

Question

I am trying to create validation so the value passed should be in format as i expect.

For example values can be 40% or 40GB.

I am trying to use the regex

(\\d*\\.?\\d*)([MB|GB|TB|PB|%]?)

Is above regex correct?

kennytm · Accepted Answer · 2011-03-28 07:45:42Z

No it's wrong.

The character class [xyz] is for matching single character. In fact, [MB|GB|TB|PB|%] means matching a single character which is one of M, B, |, G, T, P or %. Grouping should be done with (?:...) not [...].
```
((?:MB|GB|TB|PB|%)?) 
```
Of course it is better to collect the prefixes of the bytes. Also, I think the unit is mandatory, so the ? should be removed:
```
([MGTP]B|%) 
```
The regex matches an empty substring, so anything would pass, e.g. use
```
\d+(?:\.\d+)? 
```
instead.

Together:

(\d+(?:\.\d+)?)([MGTP]B|%)

@Developer: No, you need (\d+(?:\.\d+)?)([MGTP]?B|%) for 40B (and it matches the possibly invalid 4.5B.)
@Developer: In that case the whole unit is optional (\d+(?:\.\d+)?)([MGTP]?B|%)?. You know what ? means right?
@Developer: This is getting ridiculous, how is 'AS' a unit of storage size? ((\d+(?:\.\d+)?)([MGTP]?B|%|AS)?, and please do learn regex properly. All the above requests can be solved by simply adding more alternations. I will stop answering comments here for the same pattern.)

xkeshav · Accepted Answer · 2011-03-28 07:54:16Z

1

try this

^\d*([MGTP]B|%)$

answered Mar 28, 2011 at 7:48

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1 Comment

@Kenny, Thanks for the optimized way