[ale] Move last line of a file to first line

Thu Mar 29 09:01:04 EDT 2012

Thanks, although it wasn't meant to be a bat.  :)  Because ed is on plan 9,
Solaris, Linux, and Mac, out of the box and pretty consistently, I used it
as a real interactive editor for a while, after Brantley Coile told me that
using it made a difference in the way he thought about his code.

I found it to be a surprisingly useful editor and am fond of it now even
though I've gone back to using bigger, less ubiquitous interactive editors.

There's a funny page about ed that y'all might have already seen:

  http://www.gnu.org/fun/jokes/ed.msg

On Thu, Mar 29, 2012 at 8:09 AM, Jim Kinney <jim.kinney at gmail.com> wrote:

> I must now add ed to my daily tool pile. grep, awk [s]ed, vi[m], bash.
>
> That was a very good "clue bat" on why ed should still be used. a 1M line
> file would be easy for ed but pain for sed.
>
> Thanks!
>
> On Wed, Mar 28, 2012 at 9:57 PM, Ed Cashin <ecashin at noserose.net> wrote:
>
>> Thanks for mentioning the non-stream editor!  They made sed for streams,
>> because ed is for files.  It is at times like this when I sincerely regret
>> the way distros are beginning to omit ed for the first time in decades.
>>
>> There's an ed move command called "m".  Move this line to that line.  The
>> one liner below does the same thing as this interactive session
>>
>> $m0
>> w
>> q
>>
>> ecashin at reynolds:~$ head /etc/passwd | nl > ~/tmp/a
>> ecashin at reynolds:~$ cp ~/tmp/a ~/tmp/b
>> ecashin at reynolds:~$ printf '$m0\nw\nq\n' | ed ~/tmp/b
>> 414
>> 414
>> ecashin at reynolds:~$ diff -u ~/tmp/a ~/tmp/b
>> --- /home/ecashin/tmp/a 2012-03-28 21:40:25.000000000 -0400
>> +++ /home/ecashin/tmp/b 2012-03-28 21:41:44.000000000 -0400
>> @@ -1,3 +1,4 @@
>> +    10 news:x:9:9:news:/var/spool/news:/bin/sh
>>       1 root:x:0:0:root:/root:/bin/bash
>>       2 daemon:x:1:1:daemon:/usr/sbin:/bin/sh
>>       3 bin:x:2:2:bin:/bin:/bin/sh
>> @@ -7,4 +8,3 @@
>>       7 man:x:6:12:man:/var/cache/man:/bin/sh
>>       8 lp:x:7:7:lp:/var/spool/lpd:/bin/sh
>>       9 mail:x:8:8:mail:/var/mail:/bin/sh
>> -    10 news:x:9:9:news:/var/spool/news:/bin/sh
>> ecashin at reynolds:~$
>>
>> On Wed, Mar 28, 2012 at 12:41 PM, Richard Bronosky <Richard at bronosky.com>wrote:
>>
>>> Be careful doing this with large files. You are storing the whole file
>>> in memory.
>>>
>>> I would do this in 2 passes.
>>>
>>> # First get the last line into a new file. (assuming the file in
>>> question is passed in as the first argument)
>>> tail -n1 $1 > $1.mod
>>> # Second add the rest of the file, less the last line.
>>> sed '$d' $1 >> $1.mod
>>>
>>> This is working with streams. It requires an additional $filesize of
>>> disk space, but it does not require $filesize of RAM.
>>>
>>> If you want to be really efficient, use ed. ;-)
>>> # This will trim the last line of the file in place, but I'm not
>>> taking the time to figure out how to add it to the beginning.
>>> ed "$1" << EOF
>>> $
>>> d
>>> w
>>> EOF
>>>
>>> On Mar 28, 2012 11:19 AM, "Lightner, Jeff" <JLightner at water.com> wrote:
>>> >
>>> > I found this works:
>>> >
>>> > awk '{a[NR]=$0} END {print a[NR]; for (i=1;i<NR;i++) print a[i]}'
>>> originalfile >newfile
>>> >
>>> >
>>> >
>>> > Where you replace originalfile and newfile with real file names.
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > ________________________________
>>> >
>>> > From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of
>>> Lightner, Jeff
>>> > Sent: Wednesday, March 28, 2012 11:10 AM
>>> > To: Atlanta Linux Enthusiasts
>>> > Subject: [ale] Move last line of a file to first line
>>> >
>>> >
>>> >
>>> > We have variable length text files being received in which the
>>> “header” line we use in automated processing is the last line of the file
>>> rather than the first line.
>>> >
>>> >
>>> >
>>> > What is the best way to move that last line of a text file to be the
>>> first line?
>>> >
>>> >
>>> >
>>> > Please answer the question as asked and don’t suggest making the file
>>> be in the correct order when we receive it or changing the automated
>>> processing to read the last line first.  Assume those aren’t options.
>>> >
>>> >
>>> >
>>> > What I came up with was to do tail -1 >newfile and head -<number of
>>> lines – 1> but was thinking there ought to be a better way.
>>> >
>>> >
>>> >
>>> > I see sed can deal with last line, first line and insertion but the
>>> examples I’m finding address either/or not moving last line to first line.
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
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>>
>>
>>
>> --
>>   Ed Cashin <ecashin at noserose.net>
>>   http://noserose.net/e/
>>   http://www.coraid.com/
>>
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>>
>
>
> --
> --
> James P. Kinney III
>
> As long as the general population is passive, apathetic, diverted to
> consumerism or hatred of the vulnerable, then the powerful can do as they
> please, and those who survive will be left to contemplate the outcome.
> - *2011 Noam Chomsky
>
> http://heretothereideas.blogspot.com/
> *
>
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-- 
  Ed Cashin <ecashin at noserose.net>
  http://noserose.net/e/
  http://www.coraid.com/
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