string - How can join consecutive non-empty lines using sed/awk? -

how can join consecutive non-empty lines single lines using sed or awk? example given of trying do.

input:

aaa ff gg bbb eee eee ss gg dd  aaa ff gg bbb eee eee ss gg dd  aaa ff gg bbb eee eee ss gg dd 

converts

aaa ff gg bbb eee eee ss gg dd  aaa ff gg bbb eee eee ss gg dd  aaa ff gg bbb eee eee ss gg dd 

if perl okay:

$ perl -00 -pe 's/\n(?!$)/ /g' ip.txt aaa ff gg bbb eee eee ss gg dd  aaa ff gg bbb eee eee ss gg dd  aaa ff gg bbb eee eee ss gg dd 

• -00 read input in paragraph mode
  • see http://perldoc.perl.org/perlrun.html#command-switches more info , -pe options
  • use perl -i -00 -pe inplace editing
• s/\n(?!$)/ /g replace newlines except 1 blank line space