Regular Expression help needed

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I'm trying to figure out a regex that will match only a properly formatted string, and return false if any part of it is invalid.

My string is in the format of filesystem wildcards separated by a comma to allow for multiple wildcards to be put in one string. I am able to come up with a regex to match a wildcard with no problem, but I cannot get one to invalidate the whole string if anything is amiss.

For example, if "*.exe, .bat" is given, then it should be invalid because there is no * before the .bat. However my regex still turns up true because it finds the *.exe in there

(\*\.[a-zA-Z0-9]+\,?\s*)

is what I'm using.

Posted 9-Jan-12 0:43am

agent154

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2 solutions

Solution 2

Hi,
use ?(question mark) after *,*? it denote * may present or absent..try it

Posted 9-Jan-12 1:06am

mahalatchumi

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Michel [mjbohn] · Accepted Answer · 2012-01-09T01:06:00

Solution 1

There are two cases to take care of.
1) Only one search pattern
2) More than one search pattern

((^\*\.[a-zA-Z0-9]+\,\s*)*(\*\.[a-zA-Z0-9]+\s*)$)

The first part

(^\*\.[a-zA-Z0-9]+\,\s*)*

matches for zero or more patterns followed by comma and the second part

(\*\.[a-zA-Z0-9]+\s*)

for only one or the last pattern.

^ and $

are matching beginning end of string.

[Edit]
Regarding your comment I tested on RegExr. With omitting ^ and $ it worked fine. But I also found a shorter one

(\*\.[a-zA-Z0-9]+\s*\,?\s*)+

Almost the same that you came up with but this one also matches whitespace in front and behind comma.
[/Edit]

Posted 9-Jan-12 1:06am

Michel [mjbohn]

Updated 12-Jan-12 2:36am

v3

Comments

agent154 11-Jan-12 20:51pm

This seems to work, but only for two substrings. If I go beyond and add a third, then it matches only the third. I'm using http://gskinner.com/RegExr/ to test this.

Michel [mjbohn] 12-Jan-12 8:37am

I updated my solution

agent154 12-Jan-12 9:45am

You did in fact need the ^ and $. I think that might have been all I was missing. After adding those back into your modified solution, it seems to do what I want. Without it, it will still evaluate as 'true' if my first parameter is valid and the rest are not.

^(\*\.[a-zA-Z0-9]+\s*\,?\s*)+$ is what seems to work.