How to remove extra spaces in bash?

Question

How to remove extra spaces in variable HEAD?

HEAD="    how to  remove    extra        spaces                     " 

Result:

how to remove extra spaces 

Answer 1

Try this:

echo "$HEAD" | tr -s " " 

or maybe you want to save it in a variable:

NEWHEAD=$(echo "$HEAD" | tr -s " ") 

Update

To remove leading and trailing whitespaces, do this:

NEWHEAD=$(echo "$HEAD" | tr -s " ") NEWHEAD=${NEWHEAD%% } NEWHEAD=${NEWHEAD## } 

Answer 2

Using awk:

$ echo "$HEAD" | awk '$1=$1' how to remove extra spaces