Trim whitespace from middle of string

Question

I'm using the following regex to capture a fixed width "description" field that is always 50 characters long:

(?.{50})

My problem is that the descriptions sometimes contain a lot of whitespace, e.g.

"FLUID        COMPRESSOR                          "

Can somebody provide a regex that:

1. Trims all whitespace off the end
2. Collapses any whitespace in between words to a single space

Answer 1

Is there a particular reason you are asking for a regular expression? They may not be the best tool for this task.

A replacement like

 s/[ \t]+/ /g

should compress the internal whitespace (actually, it will compress leading and trailing whitespace too, but it doesn't sound like that is a problem.), and

s/[ \t]+$/$/

will take care of the trailing whitespace. [I'm using sedish syntax here. You didn't say what flavor you prefer.]

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Right off hand I don't see a way to do it in a single expression.

Answer 2

Substitute two or more spaces for one space:

s/  +/ /g

Edit: for any white space (not just spaces) you can use \s if you're using a perl-compatible regex library, and the curly brace syntax for number of occurrences, e.g.

s/\s\s+/ /g

or

s/\s{2,}/ /g

Edit #2: forgot the /g global suffix, thanks JL

Answer 3

Perl-variants: 1) s/\s+$//; 2) s/\s+/ /g;

Answer 4

str = Regex.Replace(str, " +( |$)", "$1");

Answer 5

Since compressing whitespace and trimming whitespace around the edges are conceptually different operations, I like doing it in two steps:

re.replace("s/\s+/ /g", str.strip())

Not the most efficient, but quite readable.

Answer 6

/(^[\s\t]+|[\s\t]+([\s\t]|$))/g replace with $2 (beginning|middle/end)