Regular expression for value not greater than 6 with 1 decimal place

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i have made this for 1 decimal place but don't know how to limit upto 6

accepted value
6.0
1.1
0.0
2.1
5.9

not accepted
6.1
6.01
6.2
0.00
5.99

"^[0-9]+(\.[0-9]{1,1})?$"

What I have tried:

i have made this for 1 decimal place but don't know how to limit upto 6 ^[0-9]+(\.[0-9]{1,1})?$"

Posted 27-Apr-17 21:45pm

Akhil Jain

Updated 28-Apr-17 0:01am

OriginalGriff

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Comments

Tomas Takac 28-Apr-17 4:08am

Why do you need to validate the value with the regex? It would be easier to parse the value and then check the range.

Richard MacCutchan 28-Apr-17 4:19am

Why are you allowing 0-9 as the first digit when 6 is supposed to be the limit?

4 solutions

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OriginalGriff · Answer 1 · 2017-04-27T22:25:00

Don't use a regex: Use a basic regex to process the overall format for "digit followed by optional single decimal place":

^(\d(\.\d))$

Then use Decimal.TryParse to convert it to a number, and check the bounds on that.
You can use a regex to check for 0.0 to 6.0, but it's a PITA to maintain if there is a trivial change later. Much easier to understand and modify later if you use code as well.

Jochen Arndt · Answer 2 · 2017-04-27T22:41:00

Solution 2

You have to differentiate between 6[.0] and 0[.d] to 5[.d]:

~~^(6(\.0)?)|([0-5](\.[0-9])?)$~~
^((6(\.0)?)|([0-5](\.[0-9])?))$

The above allows numbers without fractional digits. If the fractional digits must be supplied it is simpler:
~~^(6\.0)|([0-5]\.[0-9])$~~
^((6\.0)|([0-5]\.[0-9]))$

Posted 27-Apr-17 22:41pm

Jochen Arndt

Updated 27-Apr-17 23:18pm

v2

Comments

Akhil Jain 28-Apr-17 4:58am

both are accepting 6.02

Jochen Arndt 28-Apr-17 5:17am

Uups.
I forgot the surrounding parentheses.

Akhil Jain 28-Apr-17 21:51pm

not accepting 6.0

Patrice T · Answer 3 · 2017-04-28T00:01:00

Just a few interesting links to help building and debugging RegEx.
Here is a link to RegEx documentation:
perlre - perldoc.perl.org[^]
Here is links to tools to help build RegEx and debug them:
.NET Regex Tester - Regex Storm[^]
Expresso Regular Expression Tool[^]
This one show you the RegEx as a nice graph which is really helpful to understand what is doing a RegEx:
Debuggex: Online visual regex tester. JavaScript, Python, and PCRE.[^]

Akhil Jain · Answer 4 · 2017-04-27T22:42:00

Solution 3

^([0-5]\.\d|6\.0)$

i got it

Posted 27-Apr-17 22:42pm