Question

I am working on what is basically an IP detector regex.

Basically, I want to remove all numbers that do not have periods in them.

For instance, here are some sample inputs:

1          >Matches
12         >Matches
134        >Matches
156        >Matches
1567       >Matches
1.99       >No Match
.100       >Don't care
1.2.3.4    >No Match
.1.2.3.4   >No Match

This is used to remove all the matches. Matches are separated by space. For instance, if I inputted the string:

"14. 24. asf.d 7 .12 .498 .s g 14091 87.49 .sdf.gs.df 12874 ds.fgs 9.127.41 sd.fg 92.47 sd.fg 892.14 sd.fg .79 12 s.df 47 8 .sdfg 1.9 sdfg 2.4 71. s9 24 .ds.f.g 71.9 8 s.df 4 .g 7 132. .sdfg 4 s.dfg"

I might be returned something similar to the string:

"asf.d .s g 87.49 .sdf.gs.df ds.fgs 9.127.41 sd.fg 92.47 sd.fg 892.14 sd.fg s.df .sdfg 1.9 sdfg 2.4 s .ds.f.g 71.9 s.df .g  .sdfg s.dfg"

I have gotten as far as:

([0-9]+)(?=)

But I am not sure how to make the regex ignore the numbers if they have periods in them ( and actually, I am not sure how to get it to first select numbers even if they have periods in them!)

Answer 1

You could try this regular expression:

"(?<![0-9.])[0-9]+(?![0-9.])"

Explanation:

• (?<![0-9.]): Negative look behind. Previous character is not 0-9 or a dot.
• [0-9]+: One or more digits in 0-9.
• (?![0-9.]): Negative look ahead. Next character is not 0-9 or a dot.