Need help with a regular expression

Question

I am trying to use a regular expression like this:

string Size= "10.5M"; Match m = null; if ((m = (new Regex(@"(\d)([MGTP%]?)", RegexOptions.IgnoreCase).Match(Size))).Success) { Size = m.Groups[1].ToString(); if (m.Groups.Count > 1) SizeUnit = m.Groups[2].ToString(); // if not given, SizeUnit is percentage }

But when I pass the value, Size shows as 10, and SizeUnit as "" instead of the expected Size = 10.5 and SizeUnit = M

This one might work: (\d+\.\d+)([MGTP%]?)

fjdumont
– fjdumont

2011-03-18 10:52:35 +00:00
Commented Mar 18, 2011 at 10:52 — fjdumont
– fjdumont, Commented Mar 18, 2011 at 10:52

Hans Keﬆing · Accepted Answer · 2011-03-18 11:00:57Z

4

A \d doesn't match the '.'. Use [0-9]+(\.[0-9]+)? instead.

edited Mar 18, 2011 at 11:00

answered Mar 18, 2011 at 10:37

Hans Keﬆing

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Comments

R. Martinho Fernandes · Accepted Answer · 2011-03-18 10:47:16Z

The \d character class matches a digit character. To match a number with a fractional part, as in your example you will need to:

Match more than one digit: apply the + quantifier to \d;
Match the dot; since a dot has a special meaning (it matches any character), you need to escape it with a \;
Match some more digits;
Maybe make the dot and the fractional part optional, using the ? (zero or one) and * (zero or more) quantifiers, respectively.

A regular expression like this one may suit your needs:

(\d+\.?\d*)([MGTP%]?)

Sam Holder · Accepted Answer · 2011-03-18 13:30:22Z

your problem is that your expression only currently matches on a digit and not on the decimal point and following digits. This would be better I think

if ((m = (new Regex(@"(\d*\.?\d*)([MGTP%]?)", RegexOptions.IgnoreCase).Match(Size))).Success) { Size = m.Groups[1].ToString(); if (m.Groups.Count > 1) SizeUnit = m.Groups[2].ToString(); // if not given, SizeUnit is percentage }

which will match at least 0 or more digits followed by a single '.' followed by zero or more other digits.

you're right, I could use *. And I don't know what is valid and what isn't. I assumed from the example it was a number that was going to be expected, but was just trying to point out what it would and wouldn't do.

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