CODEWITHSUNDEEP
c#regex
Justin
Justin

Reputation: 3443

Regex - how do i match the first part of an indexed path

for the line

Tester[0]/Test[4]/testId
Tester[0]/Test[4]/testId
Test[1]/Test[4]/testId
Test[2]/Test[4]/testId

I want to match the first part of the path including the first [, n and ] and first / so for line above I would get 

Tester[0]
Tester[0]
Test[1]
Test[2]

I have tried using 

var rx = new Regex(@"^\[.*\]\/");
var res = rx.Replace("Tester[0]/Test[4]/testId", "", 1 /*only one occurrence */);

i get 

res == "testId";

rather than 

res == "Test[4]/testId"

which is what im hoping for so its matching the first open square bracket and the last closing bracket. I need it to match only the first closing bracket

Update: Sorry, i am trying to match the first forward slash also.

Tester[0]/
Tester[0]/
Test[1]/
Test[2]/

Solution: to remove the first match using "?":

var rx = new Regex(@"^.*?\[.*?\]\/");
var res = rx.Replace("Tester[0]/Test[4]/testId", "", 1 /*only one occurrence */);

Upvotes: 1

Views: 536

Answers (3)

treeseal7
treeseal7

Reputation: 749

Is this the sort of thing you are looking for?

updated

var str="Tester[0]/Test[4]/testId\nTester[0]/Test[4]/testId\nTest[1]/Test[4]/testId\nTest[2]/Test[4]/testId"

console.log(str)
//  Tester[0]/Test[4]/testId
//  Tester[0]/Test[4]/testId
//  Test[1]/Test[4]/testId
//  Test[2]/Test[4]/testId

var str2=str.replace(/\/.+/mg,"")

console.log(str2)
//  Tester[0]
//  Tester[0]
//  Test[1]
//  Test[2]

this works by starting the match at the first '/' and then ending when the line ends and replaces this match with " ". the m flags multi-line and the g flags to do a global match.

Upvotes: 0

Akash KC
Akash KC

Reputation: 16310

You can use lookahead and lookbehind approach to find matching and replace accordingly :

With lookaround approach, your regex would be like this :

(?=/).*(?<=])

Upvotes: 0

Cy Rossignol
Cy Rossignol

Reputation: 16817

I'm assuming this was your original regex pattern: ^.*\[.*\]/ (the pattern in your question does not match the lines).

This pattern uses greedy quantifiers (*), so, even though we only requested one match, the pattern itself matches more than we'd like. As you noticed, it matched until the second occurrence of the square brackets.

We can make this pattern non-greedy by adding question marks to the quantifiers: ^.*?\[.*?\]/.

Although this works for your use-case, a better pattern may be: ^[^/]+/. This removes any character up to the first forward-slash. The [^ ... ] is a negative character class (the brackets are unrelated to the brackets in the strings we're matching against). In this case, it matches any character that isn't a forward-slash.

For this simple text manipulation, though, we could just use a String.Substring() instead of regular expressions: 

line.Substring(line.IndexOf('/') + 1);

This is faster and easier to understand than a regular expression pattern.

Upvotes: 1

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