How to enclose every line in a file in double quotes with sed?

You almost got it right. Try this slightly modified version:

sed 's/^.*$/"&"/g' file.txt

shorter

sed 's/.*/"&"/'

without spaces

sed 's/ *\(.*\) *$/"\1"/'

skip empty lines

sed '/^ *$/d;s/.*/"&"/'

here it is

sed 's/\(.*\)/"\1"/g'

Related