How to replace space with one blank with sed?

Question

Using sed "s / [[: blank:]] * // g" a> b doesn't seem to work.

Answer 1

You need to change the asterisk to a plus sign:

sed "s/[[:blank:]]\+/ /g" a>b

or use an alternative that means the same thing:

sed "s/[[:blank:]][[:blank:]]*/ /g" a>b

or

sed "s/[[:blank:]]\{1,\}/ /g" a>b

In addition, it is more useful to send error messages or the exact ways in which the behavior differs from expectations, since “it seems that it does not work” conveys very little information.