How do I match a regex when it appears at the start of a line, even when it might not necessarily be at the start of the string?

I need to mask the credit card (if digits >=12 and <=19) and account number (if digits == 8 or 9). Following should be input/output for various strings–

I need to mask the last 4 digits but not hyphen (-) in a credit card number.

I’ve a string like this,

I want to find log files ending with “access” and a number, such as 500m-access0.log.
My code :

This regular expression '(?:[sdmt]|ll|ve|re)| ?p{L}+| ?p{N}+| ?[^sp{L}p{N}]+|s+(?!S)|s+ works as expected to match Ġmeousrtr, this can be seen in the shared link https://regex101.com/r/UR0P6T/1

I want to split a semicolon-separated test string with a regular expression in C#.
I know I could use for this example the string split method but the pattern and input string is a bit more complicated and I want to keep it simple.

I make a string pattern in c# is

I’m trying to validate some user input for the country code of a phone number. The country code is optional, but when it contains a value it should be 1 to 4 digits. I wrote a regular expression and expected the regular expression to fail when passing "n" in C#. It appeared to match, so I popped open the C# interactive console in Visual Studio 2022 (version 17.8.6). Indeed, the pattern was matching a newline character unexpectedly. My experiments below:

myPattern = @”?:[.]?[d]+(?:[,.]*d)*”; However, I would like to exclude the numbers following the dollar sign ($), and want to exclude numbers in parentheses (){}[]. For example: input text (match) —————————– abc123,000.5xyz (match:123,000.5) abc.5xyz (match:.5) abc0.2xyz (match:0.2) abc123.2xyz (match:123.2) abc$123xyz (false) abc(123)77xyz (match:77) abc12{123}xyz (match:12) abc[123]xyz (false) c# regex You can use this regex: (?<![${([d])d+(,d{3})*(.d+)?(?![]})]) It […]