penultimate line script

On 21 Dec 2005 at 11:01, Angus Leeming wrote:

> Eric Pement wrote:
[ ... ]

> >  The following sed script will print
> > the penultimate line (the next to last line) on a file of any length
> > except a file which has only one line, in which case it prints
> > nothing:
> > 
> >    sed -e '$!{h;d;};x'
> 
> How about adding
> 
> 1{
>   ${
>     p
>     q
>   }
> }
> 
> To overcome that limitation?

Well, that would depend on what the user wanted to do with one-line 
input; some would want nothing to be printed, others might want the 
last line printed anyway. I guess I could put *both* of them in the 
one-liners file and let the user decide.

For your recommended script, it would work at the end of the file. A 
bit more efficient would be to put it at the head of the script, 
where it could be reduced to:

   sed '1{$q;};$!{h;d;};x' file

in GNU syntax. I'm not sure how to break it up for other seds.

-- 
Eric Pement - pemente@xxxxxxxxxxxxx
home page: http://www.pement.org
2 Cor. 4:5




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