Re: Not a bug, a wish

[Martin Bernreuther]

Hello,

Am Mittwoch, 26. März 2008 schrieb Micah Cowan:
> > I thank you very much for devolopping coreutils that allows quick and
> > simple replacement of SQL queries and check. What I would appreciate is
> > a tool that does head and tail in one command, giving the top and bottom
> > lines from a piped output.

I also think that such a command would be easier to use than head and tail,
which both just extract lines from a stream and therefore do a similar thing.

> Do you literally mean just the one top line and one bottom line? That
> could easily be achieved with the sed command: sed -n '1p;$p'.

Nice.

In my case I often want to extract some part of a file (or stream).
Consider something like
        headtail 3:5 inputfile
and
        head -n 5 inputfile | tail -n $[5-3+1]
The first version would be "easier to understand" and might
be more efficient to implement.
(I found the pipe mechanism for file sizes >100 GB not very reliable.)
Often you like to remove a header...
A negative number is sometimes used in scripting-languages
to mark or count from the end of the file like
        headtail 2:-1 inputfile
To just remove the first line a combination of tail and wc
theoretically would work (quite inefficient)
        tail -n $[`wc -l <inputfile`-1] inputfile
You might also want to remove a footer like
        headtail 2:-2 inputfile
Using head and tail: How does that work (with n header lines and m footer 
lines)?

Is there another easy way to do it? Is "sed" the command the way to go?

> If you need more lines, sed can still do it, but requires a bit more
> work. You might look to a simple solution in
> awk/Perl/your-scripting-language-of-choice.

No!!! I definitely don't want to use Perl or "my-scripting-language-of-choice"
for such an easy task. What is the sense of these tools then?
You probably master most of the coreutil-tasks also with these
scripting-languages-of-choice, don't you?

Martin Bernreuther
-- 
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Martin Bernreuther      address@hidden