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

Try this one:

echo '    how to  remove    extra        spaces                     ' | sed 's/^ *//g' | sed 's/$ *//g' | sed 's/   */ /g'

or

HEAD="    how to  remove    extra        spaces                     "
HEAD=$(echo "$HEAD" | sed 's/^ *//g' | sed 's/$ *//g' | sed 's/   */ /g')