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

Thu Mar 29 00:29:51 EDT 2012

Sadly, I only know "of" ed. But, thanks to you, Ed, I'm now interested
in using ed in my daily workflow. I like this particular use case.
I've added it to my gist.
https://gist.github.com/2228256#file_flop2.sh (I <3 heredoc syntax)

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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-- 
.!# RichardBronosky #!.