Date: Tue, 07 Nov 2017 11:54:03 -0700 From: JD <jd1008@gmail.com> To: freebsd-questions@freebsd.org Subject: Re: sed - remove nul lines from file Message-ID: <5A02014B.3050804@gmail.com> In-Reply-To: <f1f862f2f9cf02c5040c7c1acfa77d89.squirrel@webmail.harte-lyne.ca> References: <b21bf201363c34a90ab55c4a05ff8fd7.squirrel@webmail.harte-lyne.ca> <88a59a82-2902-9f63-0a94-bd23b910e7ad@gmx.com> <c2b1ffce6933bcb8f47c856a40d29b16.squirrel@webmail.harte-lyne.ca> <f51d6c8a-c91c-dc7c-6134-e276ec60b179@gmx.com> <88b1870184a8810072fe503917cd86be.squirrel@webmail.harte-lyne.ca> <c00693b7-ae1b-4aa8-49e2-81296cfb281f@gmx.com> <656b08b1-b79d-8e7e-27ec-e39d883f2355@gmx.com> <f1f862f2f9cf02c5040c7c1acfa77d89.squirrel@webmail.harte-lyne.ca>
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On 11/07/2017 11:46 AM, James B. Byrne via freebsd-questions wrote:
> On Tue, November 7, 2017 13:28, Yuri Pankov wrote:
>> On Tue, 7 Nov 2017 21:20:40 +0300, Yuri Pankov wrote:
>>> On Tue, 7 Nov 2017 13:14:08 -0500, James B Byrne Via
>>> Freebsd-questions
>>> wrote:
>>>> On Tue, November 7, 2017 13:03, Yuri Pankov wrote:
>>>>
>>>>> You want /d, not /g, to delete the *lines* which contain NUL
>>>>> symbols
>>>>> (that's what your subject line said).
>>>>>
>>>> Sigh. Thank you. That works. However, it also deletes any line
>>>> that
>>>> has even one NUL in it regardless of the presence of other non-nul
>>>> characters on the line.
>>>>
>>>> What I wish to accomplish is to delete only the lines that are
>>>> completely nul. I thought that this could be accomplished by
>>>> prefacing the match sting with the start of line anchor ^ and
>>>> ending
>>>> it with the end of line anchor $ but this does not work as I
>>>> expect.
>>> "[[.NUL.]]" is just a character specified by its collation name, so
>>> treat as any other ordinary character:
>>>
>>> sed -E '/^[[.NUL.]]+$/d' INFILE > OUTFILE
>>>
>>> Need extended regexp here for '+' to work.
>>
>> Or, after looking at re_format(7), it could be written using BREs,
>> your
>> choice :-)
>>
>> sed '/^[[.NUL.]]\{1,\}$/d'
>>
> sed '/^[[.NUL.]]\{0,\}$/d' INFILE > OUTFILE
>
> Which has no effect. OUTFILE and INFILE remain identical. I get the
> exact same result from the first invocation as well. Likewise:
>
> sed '/^[[.NUL.]]\{1,\}$/d' INFILE > OUTFILE
>
> and
>
> sed -E '/^[[.NUL.]]+$/d' INFILE > OUTFILE
>
> # diff INFILE OUTFILE
> #
> # ll INFILE OUTFILE
> -rw-r--r-- 1 root wheel 61480 Nov 7 13:09 INFILE
> -rw-r--r-- 1 root wheel 61480 Nov 7 13:38 OUTFILE
>
>
> I had actually tried these combinations, or at least I believe that I
> tried these, before I wrote. Given the complexity and arcane nature
> of whatever flavour of RE one is working with I may have transgressed
> and written them slightly differently. But the examples you provided
> me with give the results I obtained exactly.
>
Did you try tr -d that I posted earlier?
tr -d works just fine. To wit:
$ cat -v /tmp/x
################################################
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^
$ tr -d '\000' < /tmp/x > /tmp/x2
$ cat -v /tmp/x2
################################################
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