Re: tail -f and pipes with bash shell

[Lev Bishop]

On 19/05/05, Igor Pechtchanski  wrote:
> On Thu, 19 May 2005, Dave Korn wrote:
> >   Amusingly enough, those were still both legitimate email addresses even
> > after he X'd them out!

oops. 
 
> That's why one ought to X out the top-level suffix too.  I don't believe
> .XXX is a valid suffix.  Or get a client that munges the addresses -- I'm
> surprised this wasn't requested (or implemented) for Yahoo/GMail yet.

I requested it from gmail a long time ago (and another time after this
last event) but nothing so far...

Lev

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RE: tail -f and pipes with bash shell

[Igor Pechtchanski]

On Thu, 19 May 2005, Dave Korn wrote:

> Original Message
> >From: Lev Bishop
> >Sent: 12 May 2005 23:56
>
> > On 12/05/05, Lev Bishop  wrote:
> >> On 11/05/05, Peter Ekberg  wrote:
> >  
> > Sorry, sorry, sorry.
> >
> >  'kin gmail.
> >
> > Lev
>
>   Amusingly enough, those were still both legitimate email addresses even
> after he X'd them out!

That's why one ought to X out the top-level suffix too.  I don't believe
.XXX is a valid suffix.  Or get a client that munges the addresses -- I'm
surprised this wasn't requested (or implemented) for Yahoo/GMail yet.
Igor
-- 
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RE: tail -f and pipes with bash shell

[Dave Korn]

Original Message
>From: Lev Bishop
>Sent: 12 May 2005 23:56

> On 12/05/05, Lev Bishop  wrote:
>> On 11/05/05, Peter Ekberg  wrote:
>  
> Sorry, sorry, sorry.
> 
>  'kin gmail.
> 
> Lev


  Amusingly enough, those were still both legitimate email addresses even
after he X'd them out!


[EMAIL PROTECTED] ~> whois .com

Whois Server Version 1.3

Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.

   Domain Name: .COM
   Registrar: REGISTER.COM, INC.
   Whois Server: whois.register.com
   Referral URL: http://www.register.com
   Name Server: DNS01.GPN.REGISTER.COM
   Name Server: DNS02.GPN.REGISTER.COM
   Name Server: DNS03.GPN.REGISTER.COM
   Name Server: DNS04.GPN.REGISTER.COM
   Name Server: DNS05.GPN.REGISTER.COM
   Status: ACTIVE
   Updated Date: 12-jan-2005
   Creation Date: 18-feb-1996
   Expiration Date: 19-feb-2006

[...SNIP boilerplate...]

   Organization:
  Web Traffic Sales
  The Manager Sales Department
  Web Traffic Sales
  San Francisco, CA 9
  US
  Phone: 415-555-2398
  Email: trafficsales (AT) subliminalnetworks (DOTCOM)

   Registrar Name: Register.com
   Registrar Whois...: whois.register.com
   Registrar Homepage: http://www.register.com

   Domain Name: .COM

  Created on..: Sun, Feb 18, 1996
  Expires on..: Sun, Feb 19, 2006
  Record last updated on..: Mon, Feb 09, 2004

   Administrative Contact:
  Web Traffic Sales
  The Manager Sales Department
  Web Traffic Sales
  San Francisco, CA 9
  US
  Phone: 415-555-2398
  Email: trafficsales (AT) subliminalnetworks (DOTCOM)

   Technical Contact:
  Web Traffic Sales
  The Manager Sales Department
  Web Traffic Sales
  San Francisco, CA 9
  US
  Phone: 415-555-2398
  Email: trafficsales (AT) subliminalnetworks (DOTCOM)

   Zone Contact:
  Web Traffic Sales
  The Manager Sales Department
  Web Traffic Sales
  San Francisco, CA 9
  US
  Phone: 415-555-2398
  Email: trafficsales (AT) subliminalnetworks (DOTCOM)

   Domain servers in listed order:

   DNS17.REGISTER.COM216.21.234.79
   DNS18.REGISTER.COM216.21.226.79


[EMAIL PROTECTED] ~> whois .se

[...SNIP boilerplate...]

*domainname.name:.se
*domainname.status:  REGISTRERAT

*domainname.dns.data:
.se. NS ns.talkactive.net.
.se. NS ns2.talkactive.net.
.se. NS vennely.jth.net.

# More information is available from the Web Search,
# , but the number
# of queries to the Web Search is limited. Misusers will
# be blocked.

[EMAIL PROTECTED] ~>






cheers,
  DaveK
-- 
Can't think of a witty .sigline today


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RE: tail -f and pipes with bash shell

[Peter Ekberg]

Lev Bishop wrote:
> Try "grep --line-buffered" to get grep to flush output after every
> line. There is a performance penalty for doing this. I don't know why
> you don't see the buffering when grep's stdout isn't redirected.
> Perhaps grep (or the std library) removes/reduces buffering in the
> case the output is a terminal.
> 
> Lev

Yes, that works for this slimed down example, but probably not for
the real work, as that includes several other commands that do
not all have a --line-buffered equivalent. Thanks for you time
though.

I'll drop this now, it's getting more complex than the task
deserves. I can get by as is...

Cheers,
Peter

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Re: tail -f and pipes with bash shell

[Lev Bishop]

Try "grep --line-buffered" to get grep to flush output after every
line. There is a performance penalty for doing this. I don't know why
you don't see the buffering when grep's stdout isn't redirected.
Perhaps grep (or the std library) removes/reduces buffering in the
case the output is a terminal.

Lev

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RE: tail -f and pipes with bash shell

[Peter Ekberg]

Lev Bishop wrote:
> On 11/05/05, Peter Ekberg wrote:
>> What is going on here?
> 
> My guess: "tail frame.log" closes its stdout as soon as it has read
> the requested lines from the file, "tail -f frame.log" keeps its
> stdout open, since it is waiting for new lines to be added to the
> logfile. Cat is using some buffering on its stdin, so it tries to read
> a buffer's worth of data at a time.

Ah, thanks for the hint!

But, the buffering does not seem to happen in cat (or
is at least triggered by something external to cat).

If I open two cmd window consoles, and in the first
one I issue
~$ cat > foobar

And in the second one I issue
~$ tail -f foobar | grep d
I see all lines entered in the first console on the
second console (if they have d in them) with a fairly
rapid response time.

But if I instead issue this in the second console
~$ tail -f foobar | grep d | grep d
I get the buffering effect with high latencies...

Also, if I issue this in the second console
~$ tail -f foobar | cat
I again get a farily rapid response time.

So, the buffering does not seem to be related to cat,
but to where in the pipe the process is located, or
to the length of the pipe or something.

Rather unintuitive, my guess is that it's BYAM...

Cheers,
Peter

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Re: tail -f and pipes with bash shell

[Lev Bishop]

On 12/05/05, Lev Bishop <[EMAIL PROTECTED]> wrote:
> On 11/05/05, Peter Ekberg <[EMAIL PROTECTED]> wrote:
 
Sorry, sorry, sorry.

 'kin gmail. 

Lev

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Re: tail -f and pipes with bash shell

[Lev Bishop]

On 11/05/05, Peter Ekberg <[EMAIL PROTECTED]> wrote:
> What is going on here?

My guess: "tail frame.log" closes its stdout as soon as it has read
the requested lines from the file, "tail -f frame.log" keeps its
stdout open, since it is waiting for new lines to be added to the
logfile. Cat is using some buffering on its stdin, so it tries to read
a buffer's worth of data at a time.

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tail -f and pipes with bash shell

[Peter Ekberg]

Hello!

What is going on here?

~$ ps -f | grep $$
peda2316   1 con  20:21:51 /usr/bin/bash
peda31802316 con  21:51:47 /usr/bin/ps
peda31642316 con  21:51:47 /usr/bin/grep

  [I use bash, if that matters]

~$ tail -f frame.log | grep Antenna
2005-05-11,21:51:07: Antenna DAC 0
2005-05-11,21:51:17: Antenna DAC 0
2005-05-11,21:51:26: Antenna DAC 0
2005-05-11,21:51:36: Antenna DAC 0
2005-05-11,21:51:46: Antenna DAC 0
2005-05-11,21:52:06: Antenna DAC 0

  [Fine, that works, I get bored and press ^C]

~$ tail frame.log | grep Antenna | cat
2005-05-11,21:51:17: Antenna DAC 0
2005-05-11,21:51:26: Antenna DAC 0
2005-05-11,21:51:36: Antenna DAC 0
2005-05-11,21:51:46: Antenna DAC 0
2005-05-11,21:52:06: Antenna DAC 0

  [Fine, that works...]

~$ tail -f frame.log | grep Antenna | cat

  [No output!? I'm puzzled and press ^C]

Every other line in frame.log is an "Antenna"-
line, so I really think there should be output
from the last command as well.

(For the real task I'm doing I want to do more
 than 'cat' at the end of the pipe, this is just
 a trimmed down example.)

Can anyone please provide any hints?

Cheers,
Peter


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