Regex null char

Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Regex for not empty and not whitespace Ask Question. Asked 10 years, 2 months ago. Active 9 months ago. Viewed k times. Improve this question. James A Mohler You can use str. NarendraYadala, this will not match on tabs and other whitespace characters.

Add a comment. Active Oldest Votes. Improve this answer. In some languages e. But interesting fact is that even under this circumstances the expression will work correctly. I want it match if the string is not whitespace or empty — Dan Hastings.

Show 4 more comments. The other solution, which is used by Perl , is to always start the next match attempt at the end of the previous match, regardless of whether it was zero-length or not.

If it was zero-length, the engine makes note of that, as it must not allow a zero-length match at the same position. Thus Perl begins the second match attempt also at the start of the string.

The first alternative again finds a zero-length match. But this is not a valid match, so the engine backtracks through the regular expression. Now the second alternative in the regex is attempted. The third match attempt begins at the position after the x in the string. The first alternative matches 1 and the third match is found. After x is matched, it makes one more match attempt starting at the end of the string.

So depending on how the engine advances after zero-length matches, it finds either three or four matches. One exception is the JGsoft engine. The JGsoft engine advances one character after a zero-length match, like most engines do. But it has an extra rule to skip zero-length matches at the position where the previous match ended, so you can never have a zero-length match immediately adjacent to a non-zero-length match.

In our example the JGsoft engine only finds two matches: the zero-length match at the start of the string, and 1. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Helping communities build their own LTE networks. Podcast Making Agile work for data science.

Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Related Hot Network Questions. These expressions can be used for matching a string of text, find and replace operations, data validation, etc. For example, with regex you can easily check a user's input for common misspellings of a particular word. This guide provides a regex cheat sheet that you can use as a reference when creating regex expressions.

Consult the following regex cheat sheet to get a quick overview of what each regex token does within an expression. With the regex cheat sheet above, you can dissect and verify what each token within a regex expression actually does.

However, you may still be a little confused as to how to put these tokens together to create an expression for a particular purpose.