sed - remove nul lines from file

[Noel]

On 11/7/2017 1:09 PM, Polytropon wrote:
> On Tue, 7 Nov 2017 13:54:41 -0500, James B. Byrne wrote:
>> On Tue, November 7, 2017 13:36, Polytropon wrote:
>>> On Tue, 7 Nov 2017 12:12:55 -0500, James B. Byrne via
>>> freebsd-questions wrote:
>>>> I have a data file created by an ancient proprietary scripting
>>>> language called QTP.  There is a bug in this program which, on
>>>> occasion, manifests itself by inserting output records consisting
>>>> entirely of nul (^@) (\x00) bytes at regular intervals.  In the
>>>> present case every 47th. record consists entirely of nuls.
>> ...
>>> In this case, awk can also help:
>>>
>>> 	$ awk '(length > 0)' < infile.txt > outfile.txt
>>>
>>> This will print all lines which are longer than 0 characters.
>>>
>> Thank you very much. This worked exactly as I required.
>>
>> I infer from this that awk does not consider nul a character and its
>> presence does not count towards the length of a record.  Which is
>> counter intuitive to me.  A nul takes up the same space as any other
>> character so why is it not counted?  I would not have tried this
>> construction for that reason.
> Even though this example was actually meant for empty lines,
> i. e., those where the NULs have already been removed (for
> example with the tr -d command), but it seems that awk does
> actually ignores the NULs.
>
> Let's say this is the test input:
>
> 	foo
> 	bar
> 	^@^@^@^@^@^@^@^@
> 	baz
> 	meow
>
> When fed into the awk command mentioned above, the NULs are
> magically removed:
>
> 	$ awk '(length > 0)' < nul.txt 
> 	foo
> 	bar
> 	baz
> 	meow
>
> This is an interesting behaviour, but fits the current problem
> quite well: It removes NULs and emoty lines. :-)
>
>
>
>
>


I'd probably just use grep.

grep '^[[:print:]]'  INFILE  >   OUTFILE

ie. any line that starts with a printable character is copied to
OUTFILE.  This will skip all-null and empty lines.