topic Re: tail command foo in Operating System - HP-UX

tail command foo

jerry1 — Wed, 08 Sep 2004 16:15:41 GMT

Why does tail only tail 703 lines to a file.

If I tail -5000 a file that has 50000 lines
I get 5000 lines.

If I tail -5000 and redirect > to another
file name I only get 703 lines.

Does anyone know why?

Re: tail command foo

John Poff — Wed, 08 Sep 2004 16:22:16 GMT

Hi,

The 'tail' command actually has a 20K byte buffer, which will limit the actual number of lines you can get from it, depending on the size of your lines.

You might want to use Perl or awk to see if you can get what you need.

JP

Re: tail command foo

John Poff — Wed, 08 Sep 2004 16:25:56 GMT

From the 'tail' man page:

" Tails relative to end-of-file are stored in a 20-Kbyte buffer, and
thus are limited in length. Therefore, be wary of the results when
piping output from other commands into tail."

JP

Re: tail command foo

Sยภเl Kย๓คг — Wed, 08 Sep 2004 23:24:52 GMT

yes it is a problem of tail buffer size limitation
regards
SK

Re: tail command foo

jerry1 — Thu, 09 Sep 2004 07:23:54 GMT

Can tail be modified to output more lines?

Re: tail command foo

Pete Randall — Thu, 09 Sep 2004 07:28:07 GMT

Sorry, no. However you could try something with sed like this:

# print last 10 lines of file (emulates "tail")
sed -e :a -e '$q;N;11,$D;ba'

Change the "11" to whatever number you're trying to retrieve.

Pete

Re: tail command foo

Henry Chua — Thu, 09 Sep 2004 09:33:52 GMT

As said, tail has a limited buffer..
awk will be the answer.. its really powerful

Re: tail command foo

Muthukumar_5 — Thu, 09 Sep 2004 10:53:21 GMT

You can use awk as,

awk '{ if ( NR >= 10 ) print $0 }' file

So that it will print the liens after line number 10 there

Re: tail command foo

Muthukumar_5 — Thu, 09 Sep 2004 11:31:00 GMT

Attachment a shell script, it will be helpful to get less lines on standard ouput and to get files.

Try to create a file as,

vi /usr/bin/less

chmod 755 /usr/bin/less

You can test as,

echo "bye\nfor\nnow" | less 2

It will give
for
now there.

You can test the files too as,

less 2 /usr/bin/less
# Normal end
exit 0

It will be used there. You can edit to make it efficient more.

HTH.
-Muthu

Re: tail command foo

subbukns — Tue, 26 Sep 2006 07:25:31 GMT

Hi Pete

sed -e :a -e '$q;N;'$cnt',$D;ba' abc.txt > xyz.txt

Could you please explain me the above statement -- phrase wise.

as early as possible.

Thanks,
Subbu

Re: tail command foo

jerry1 — Tue, 26 Sep 2006 08:48:47 GMT

There is a patch for tail.

Re: tail command foo

Bill Hassell — Tue, 26 Sep 2006 11:18:29 GMT

The patches are:

11.23 - PHCO_31564
11.11 - PHCO_27138
11.00 - none
10.20 - none

none = no patch, tail is limited to 20K bytes of data (not lines) and cannot be changed.