Question

Yoav – edited to be clearer

Hi,
I need to find 6 digit numerical strings in a text file. I’m working in C#.
Example:

text text text123365 text text text

The expression must skip strings longer then 6:

text text text1233656 text text text

The above string should not return any result because the length of the digit string is 7.

I came up with this expression: [^0-9]([0-9]){6}[^0-9]

It works perfectly with the exception of string that are at the start or end of the line

123365text text text text text text
text text text text text text123365

Is it possible to identify these cases?

Answer 1

Try:

(?<!\d)\d{6}(?!\d)

It says:

• Find 6 digits that are not directly preceeded or succeeded with a digit

It will look anywhere in the string.

Examples:

123365text text text text text text
text text text text text text123365

Matches:

1. 123365
2. 123365

123365text text text 234098 text text text
text text text text text 567890 text123365

Matches:

1. 123365
2. 234098
3. 567890
4. 123365