Regular expressions to match these pdf file names

Question

I am looking for a regular expression to match the fileNamePattern. Files are pdf can have these names: 8 alphanumeric chars, -, 4 alphanumeric chars, -, 4 alphanumeric chars, -, 4 alphanumeric chars, -, 12 alphanumeric chars + .pdf.

Examples:

5b7f991f-0726-4dd5-856e-7cea820f02c5.pdf
138bcee6-db7f-47a7-97bf-69c0b3989698.pdf
e988315b-ade7-48e5-9733-35bb59a3c28d.pdf

I am using

^[A-Z][0-9]{8}[-][A-Z][0-9]{4}[-][A-Z][0-9]{4}[-][A-Z][0-9]{4}[-][A-Z][0-9]{12}[.]pdf

However, I am not sure it is correct as I get no matches.

^[A-Z][0-9]{8}[-][A-Z][0-9]{4}[-][A-Z][0-9]{4}[-][A-Z][0-9]{4}[-][A-Z][0-9]{12}[.]pdf — user2897967, Mar 04 '19 at 19:00
Do not use `\w`, it also [matches underscores and a lot of other chars](https://docs.microsoft.com/en-us/dotnet/standard/base-types/character-classes-in-regular-expressions#WordCharacter) in .NET. See [my answer](https://stackoverflow.com/a/54989965/3832970) with all the explanations and exact solution. [`\d` also matches](https://stackoverflow.com/questions/16621738) a lot of chars you do not expect. — Wiktor Stribiżew, Mar 04 '19 at 19:11
BTW, you may use http://regex101.com (to manually create) and http://regexstorm.net/tester (to see if they work in .NET) to test regexps. — Wiktor Stribiżew, Mar 04 '19 at 19:17
Glad it worked for you. Please also consider upvoting if my answer proved helpful to you. — Wiktor Stribiżew, Mar 06 '19 at 12:59

score 1 · Answer 1 · answered Mar 04 '19 at 19:06

Regex r = new Regex(@"^\w{8}-\w{4}-\w{4}-\w{4}-\w{12}\.pdf$");

If you explicitly don't want underscores, you can use:

^[a-zA-Z\d]{8}-[a-zA-Z\d]{4}-[a-zA-Z\d]{4}-[a-zA-Z\d]{4}-[a-zA-Z\d]{12}\.pdf$

Regex is case-sensitive (unless you specify it to ignore case using RegexOptions. Right now the main issue is that your regex is saying to match a letter then match n digits instead of matching n alphanumeric characters.

With setting the case insensitive flag, your regex can simplify to:

^[A-Z\d]{8}-[A-Z\d]{4}-[A-Z\d]{4}-[A-Z\d]{4}-[A-Z\d]{12}\.pdf$

score 0 · Answer 2 · answered Mar 04 '19 at 19:06

0

This should work /(\w{8})-(\w{4})-(\w{4})-(\w{4})-(\w{12})(.pdf)/i

I tried it at here at RegEx Testing

\w = alphanmumeric {n} = times the sign should appear

gi = are flags: "i" = case insensitive.

answered Mar 04 '19 at 19:06

S.H

365
3
13

1

In C#, regex patterns are not defined with flags like this, `g` modifier is not supported, regex literal notation is not used. – Wiktor Stribiżew Mar 04 '19 at 19:13

score 0 · Accepted Answer · answered Mar 04 '19 at 19:07

You only match uppercase letters in your regex, and when you use [A-Z][0-9]{4} you do not match four alphanumeric chars, you match a letter followed with 4 digits.

So, you need to merge [A-Z][0-9] into single character classes [A-Z0-9] and then use a case insensitive flag.

Also, you need to use $ at the end of the regex to make the pattern match the entire string.

Use

^[A-Z0-9]{8}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{12}[.]pdf$

See the regex demo

In C#,

var rx = new Regex(@"^[A-Z0-9]{8}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{12}[.]pdf$", RegexOptions.IgnoreCase);

Note that case insensitivity can be set with an inline modifier (?i):

var pattern = @"(?i)^[A-Z0-9]{8}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{12}[.]pdf$";
// check if the string matches the pattern
if (Regex.IsMatch(s, pattern) 
{
    // The string matches...
}

Regular expressions to match these pdf file names

3 Answers3