Question

I would like to delete every double space in a file open in vim, how is this done?

e.g delete space here

a  a

but keep the space here

a a

Answer 1

:%s/\s\{2,}//g

Where the elements are:

• %s substitute in the whole file
• \s what to substitute: a space
• \{2,} two or more occurrences
• // replace with nothing (i.e. delete)
• g do it on every occurrence on the current line (not only on the first)

The elements shall become clearer if you look at the anatomy of the substitute call:

s/PATTERN/REPLACEMENT/FLAGS

So, the PATTERN in our case is \s\{2,}, the REPLACEMENT is empty and FLAGS are just g. The range gets prefixed and is % which indicates the whole file. If you just want to do it on some lines, you could select the lines visually and then type :s....

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Edit:
In your question, you wrote that you want to

delete every double space in a file

That’s what I answered. If you want to replace two and more spaces by one, the command would be

:%s/\s\{2,}/ /g