How to remove extra spaces in bash?

Question

How to remove extra spaces in variable HEAD?

HEAD=\"    how to  remove    extra        spaces                     \"

Result:

Answer 1

Take advantage of the word-splitting effects of not quoting your variable

$ HEAD="    how to  remove    extra        spaces                     "
$ set -- $HEAD
$ HEAD=$*
$ echo ">>>$HEAD<<<"
>>>how to remove extra spaces<<<

If you don't want to use the positional paramaters, use an array

ary=($HEAD)
HEAD=${ary[@]}
echo "$HEAD"

---

One dangerous side-effect of not quoting is that filename expansion will be in play. So turn it off first, and re-enable it after:

$ set -f
$ set -- $HEAD
$ set +f