Regex to fetch value from string

Question

can you help me out to fetch some value from this string which is below

ldn2spc2.ebrd.comDiskUtilization-D(Disk) --> Disk Utilization 100 > 95
%(threshold)

I want to fetch the drive letter which before "Disk" in this case which is 'D'.

I have tried this regex

ebrd.comDiskUtilization-(\D*)\ --

which give D(Disk) but my requirement is to fetch only drive letter. Please help.

In which environment do you run your RegExp? Also see non-capturing groups https://stackoverflow.com/questions/3512471/what-is-a-non-capturing-group-in-regular-expressions — avdg, Oct 15 '19 at 10:05

Sterconium · Answer 1 · 2019-10-15T10:44:31.287

0

The right answer depends much by the RegEx engine you are using. Unfortunately sometimes it is not easy to know it.

I tested your text with the engine of PCRE 8.41 2017-07-05 and I get the 'D' with the regex:

((\w+[\.-])+)\K\w(?=\(Disk\))

But it does not work for example with Chrome's Javascript. For this instead I can use this:

(?<=(\w+[\.-])+)\w(?=\(Disk\))

Try them both and see which one works for you.

edited Oct 15 '19 at 10:44

answered Oct 15 '19 at 10:34

Sterconium

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Glad I helped! If you confirm it worked can you approve my answer? :) Also, which one of the two worked? – Sterconium Oct 16 '19 at 08:18

score 0 · Answer 2 · answered Oct 15 '19 at 12:27

It appears you are using Javascript. If my understanding is correct, this regex will only capture the drive letter as capture group 1:

ebrd.comDiskUtilization-([A-Za-z])\D*\ --

With that said, I tend to think Sterconium's solution is a better, more elegant solution. If you need the drive letter to be a capture group, you could put parenthesis around the \w - in which case it would be capture group 2.

score 0 · Accepted Answer · answered Oct 15 '19 at 17:40

In your pattern you are capturing in group 1 (\D*) matching 0+ times not a digit followed by a space and 2 dashes \ --.

Using \D will also match (Disk) as it does not contain a digit.

Note that you don't have to escape the space using a backslash and you do have to escape the dot to match it literally.

ebrd\.comDiskUtilization-([A-Z])\([^)]+\) --

In parts

ebrd\.comDiskUtilization- Match literally
( Capture group 1
- [A-Z] Match an uppercase char A-Z
) Close group
\([^)]+\) Match from an opening till a closing parenthesis using a negated character class
-- Match a space and --

The drive letter will be in capturing group 1.

Regex demo

Regex to fetch value from string

3 Answers3