views:

35

answers:

3

How to search for occurences of more than one space between words in a line

1. this is a line containing  2 spaces
2. this is a line containing   3 spaces
3. this is a line containg multiple spaces first  second   three   four

All the above are valid matches for this regex. What regex should I use?

+3  A: 
[ ]{2,}

SPACE (2 or more)

You could also check that before and after those spaces words follow. (not other whitespace like tabs or new lines)

\w[ ]{2,}\w

the same, but you can also pick (capture) only the spaces for tasks like replacement

\w([ ]{2,})\w

or see that before and after spaces there is anything, not only word characters (except whitespace)

[^\s]([ ]{2,})[^\s]
Alexander
`\w` means 'word characters', that is, alphanumeric and underscore, but not other non-space characters. To check for non-whitespace, use `\S` (capital S). Also, the first one will only match lines that contain two or more spaces and nothing else.
tdammers
I tried to evolve the question. I understood that I missed what you said with `\S`, I just prefer not to rely on character case for such functionality, it's easier to read.
Alexander
Why are you using anchors at all? He's looking for spaces embedded somewhere in the lines.
Tim Pietzcker
no particular reason. At first I thought I needed them, so I dragged them all along the process. In fact, you are right that I am wrong for using them in this case. I'll edit my answer right away.
Alexander
`\w[ ]{2,}\w` will fail to match `word.<2 spaces>more words` or a string that consists entirely of spaces. `[^\s]([ ]{2,})[^\s]\w` will fail on lines that start with spaces or strings like `bla<2 spaces>.`...
Tim Pietzcker
at the moment it wasn't clear what the question was about. Finding spaces between words only (second regex), free spaces (first regex), or spaces between non-whitespace characters (last regex). Only the first regex checks for spaces regardless of whether they are preceded or followed by non-whitespace chars (including newlines). I specified it clearly in my answer. The question was too vague to give one single, definitive answer.
Alexander
Please READ the question.
Alexander
You are right, he *is* asking for "between words". Sorry, and thanks for making me aware of this. +1 for your answer then, but you still might want to point out that your second and third regex won't catch leading and trailing whitespace. Which might not be a problem for the OP.
Tim Pietzcker
+1  A: 

Simple solution:

/\s{2,}/

This matches all occurrences of one or more whitespace characters. If you need to match the entire line, but only if it contains two or more consecutive whitespace characters:

/^.*\s{2,}.*$/

If the whitespaces don't need to be consecutive:

/^(.*\s.*){2,}$/
tdammers
the `.*` is usually greedy, meaning that it will reach the end of the tested string, and all which follows, if there are mandatory characters, won't match. Usually in this case it's a good practice to add `?` , like this `.*?`. It happened to me using PHP's PCRE
Alexander
It does match. "Greedy" means that it matches as much as possible while still matching the pattern as a whole. `/^.*b.*$/` does in fact match `"foobar"`, even though you'd expect the first greedy `.*` to match the entire string already.
tdammers
+1  A: 

Search for [ ]{2,}. This will find two or more adjacent spaces anywhere within the line. It will also match leading and trailing spaces as well as lines that consist entirely of spaces. If you don't want that, check out Alexander's answer.

Actually, you can leave out the brackets, they are just for clarity (otherwise the space character that is being repeated isn't that well visible :)).

The problem with \s{2,} is that it will also match newlines on Windows files (where newlines are denoted by CRLF or \r\n which is matched by \s{2}.

If you also want to find multiple tabs and spaces, use [ \t]{2,}.

Tim Pietzcker
`more than one space between words in a line`. How is `[ ]{2,}` between words? Have you even read the question?
Alexander
Which is why I have referred to your answer in case the OP really wants to be as strict as he is writing. Maybe we should ask him.
Tim Pietzcker