Regular Expression to Match Past Label Including Empty String

Regular Expression to Match Past Label Including Empty String

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Using a regular expression, I'm trying to match a label, in this case "Business Unit:", followed by one or more spaces, then match everything in a submatch after that to the end of that line. I'm having a problem when there are no characters after the label on the line, it grabs the next line.

For example, here's some test data:

Business Unit:(space)(space)BU1(space)
This is Line 2
Business Unit:(space)(space)
This is Line 4

So I want to grab just "BU1" from the first line, and that works. It should match an empty string from the third line, but it matches the contents of the fourth line instead, in this case "This is Line 4".

Here is my expression:

Business Unit:\s+(.+)

I thought the dot character is not suppose to match a newline, but it seems like it is.

What's the correct regular expression in this case?


The real problem here is that \s+ is greedy, so it will match all whitespace (including new lines), so it matches up until the next line and then .+ catches the rest.

This should meet your requirements.

The pattern is ^Business Unit: *([\S]*)

This is assuming of course your business unit won't contain any spaces. If it does, then I can modify the pattern.

Regular Expression to Match Past Label Including Empty String, Using a regular expression, I'm trying to match a label, in this case "Business Unit​:", followed by one or more spaces, then match everything in a  There are lots of posts about regexs to match a potentially empty string, but I couldn't readily find any which provided a regex which only matched an empty string. I know that ^ will match the beginning of any line and $ will match the end of any line as well as the end of the string.


It depends, a bit on the context you are using the regex in because multi-line handling may vary, but here is a start:

/^Business Unit: +([^ ]*) *$/
  1. ^ Starting from the beginning of the line,
  2. Match the literal, Business Unit:,
  3. + followed by 1 or more spaces,
  4. ([^ ]*) capture any possible non-blank stuff,
  5. *$ followed by spaces till the end of the line.

Again, depending on your context, you may need to specify the linend as \n:

/^Business Unit: +([^ ]*) *\n/

[PDF] Regular Expressions: The Complete Tutorial, Matching Floating Point Numbers with a Regular Expression . expression (​replace the first \b with ^ and the last one with $) can be used by a “character” position in an empty string: the void after the string. So our regex will match a tag. I try to make a regular expression in a .htaccess file, that matches only an empty string. I have tried many things, but it seems like it’s impossible. For example, I tried ^$, but it's looking for "" that will always exist in a string. So I seek answers to it all possible.


The \n character is part of \s. That is why you get a match onto the following line.

You can do:

/^Business Unit:[ \t]*([^\n]*?)[ \t]*$/m

Demo

If you want to exclude the leading horizontal spaces and not match if blank:

/^Business Unit:[ \t]+(\S+)[ \t]*$/m

Demo

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Use a character class substraction for whitespace except newlines:

Business Unit:[\s&&[^\n]]*(\S*)

See live demo.

The expression [\s&&[^\n]] is the subtraction, then the capture is for 0 or more non-whitespace (your target).

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In your example you capture the last line because \s also matches a newline.

What you could do is replace \s+ to a whitespace and capture in a group any character zero or more times .*

You might use a word boundary \b at the start.

\bBusiness Unit: +(.*)

Update

Bases on the comments, to not match whitespace at the end of the line you could use match one or more times a non whitespace characters \S+ followed by repeated pattern that matches a whitespace or a tab [ \t] and one or more times a non whitespace character and make the group optional ?

\bBusiness Unit: +(\S+(?:[ \t]\S+)*)?

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Using Regex for Text Manipulation in Python, Now the previous regex expression matches a string with any length and any character. It will also match an empty string of length zero. To test this, update the​  Note: If the regular expression does not include the g modifier (to perform a global search), the match () method will return only the first match in the string. This method returns null if no match is found. Browser Support. string .match ( regexp) Parameter Values. Required. The value to search for, as a regular expression. Technical Details.


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