Delete empty lines from a file

Question

I need to delete empty lines from a file (with spaces only - not null records).

The following command works only for null rows, but not in case of spaces:

sed '/^$/d' filename

Can it be done using grep?

Answer 1

Use \s* for blank lines containing only whitespace:

 sed '/^\s*$/d' file 

To save the changes back to the file use the -i option:

sed -i '/^\s*$/d' file 

Edit:

The regex ^\s*$ matches a line that only contains whitespace, grep -v print lines that don't match a given pattern so the following will print all none black lines:

 grep -v '^\s*$' file

Answer 2

The POSIX portable way to do this is

sed -i '/^[[:blank:]]*$/d' file

or

grep -v '^[[:blank:]]*$' file