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So I have incoming data that looks something like this:

Applications                    7 days          6 days

And I'm trying to create regex that will match this line but not a line that has another column, like this:

Applications                    7 days          6 days        5 days

The regex that I'm trying to use is:

^(.*?)(\s){4,}(.*?)(\s){4,}[^(\s){2}]+

Where [^(\s){2}]+ would mean selecting everything up to a double space. The problem with this is that

  1. it doesn't work to begin with.
  2. the second line I have would still match this.

Is there any regex I can use to only match the 3 column table and not the 4 column, 5 column, etc.?

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2
  • I would go about it differently and just test by splitting each line on \s{2,} then checking that the length of the array is equal to 3. Commented May 16, 2014 at 16:40
  • is this space or tab-delimited string? Commented May 16, 2014 at 16:40

2 Answers 2

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You should take care with character classes ([]) as some chars inside are treated literally (as if they were escaped).

Try this regex (demo here):

^((?:(?!\s\s).)+)(?:\s){4,}((?:(?!\s\s).)+)(?:\s){4,}((?:.(?!\s\s))+)$
  • I switched the (.*?) with ((?:(?!\s\s).)+) which will match everything up to a sequence of two spaces.
  • I added a $ at the end, so it wouldn't match the lines with more than two columns.
  • I also added some ?: so the groups would become non-matching groups.
  • Finally, I removed the character class from the end of the regex and added a negative look-ahead.

Columns not ending with spaces

This one will not accept lines where the second column ends with spaces (demo here):

^((?:(?!\s\s).)+)(?:\s){4,}((?:(?!\s\s).)+)(?:\s){4,}((?:.(?!\s\s)(?!\s$))+)$

Notice the addition of a second negative look-ahead in the last group: (?!\s$).

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5 Comments

The only problem with that is that if there is more than 2 spaces after the end of the line it will still match it. Is there anyway for that to look ahead for 2 OR MORE spaces? Would it be as simple as adding a quantifier in the negative lookahead at the end?
I added another negative-lookahead so it won't match lines ending with spaces.
This is awesome! It works very well! May I ask some questions on it? What does the ?: do in regex?
Sure. The ?: is used to make the group a non-capturing group. For instance, if you have a regex like (.*?)(a){2}(.*?)(b){2}, when you "run" it in a string like 123aa789bb the matched groups (important in replacing) will be: 1-123, 2-aa, 3-789 and 4- bb. Now, maybe you are just interested in the (.*?) parts in the matched groups. In that case, you use ?: in the ones you don't want, like: (.*?)(?:a){2}(.*?)(?:b){2}. This way, the matched groups in that sample string would be 1-123 and 2-789.
In other words, ?: has no effect in the regex itself, just in what it will consider to be matched groups. In your case, as you probably didn't want to reference the (\s){4,}, I used (?:\s){4,}. In the end, if what the matched groups are doens't matter to you, you can ditch ?: and let your regex be a little more readable.
0

try this :

^[^\s]*(\s{2,}[^\s].*){2,}

assuming before each column-value there is at least 2 spaces.

DEMO

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