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James B. Byrne

2014-Dec-02 18:05 UTC

[CentOS] Help with at Bash script

I am attempting to get a script borrowed from DJB to work on my CentOS-6.6
box.  Simplified it looks like this:

tcpdump -l -n -e port 53 \
  | awk '{if ($14 ~ /A.*?/) print $15}' \
  | while read domain ; do echo $domain ; done ;

The sticking point is the 'while read' construct.  Run just as
'tcpdum | awk'
I get this:

english.stackexchange.com.
www.urbandictionary.com.
www.urbandictionary.com.
www.urbandictionary.com.
www.urbandictionary.com.
api.mywot.com.
a.udimg.com.
a.udimg.com.
fonts.googleapis.com.
. . .

Run with the 'while read $domain ; do echo ' pipe nothing appears
whatsoever.
What am I doing wrong?

-- 
***          E-Mail is NOT a SECURE channel          ***
James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
Harte & Lyne Limited          http://www.harte-lyne.ca
9 Brockley Drive              vox: +1 905 561 1241
Hamilton, Ontario             fax: +1 905 561 0757
Canada  L8E 3C3

Alexander Dalloz

2014-Dec-02 19:19 UTC

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[CentOS] Help with at Bash script

Am 02.12.2014 um 19:05 schrieb James B. Byrne:> I am attempting to get a script borrowed from DJB to work on my CentOS-6.6
> box.  Simplified it looks like this:
>
> tcpdump -l -n -e port 53 \
>    | awk '{if ($14 ~ /A.*?/) print $15}' \
>    | while read domain ; do echo $domain ; done ;
>
> The sticking point is the 'while read' construct.  Run just as
'tcpdum | awk'
> I get this:
>
> english.stackexchange.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> api.mywot.com.
> a.udimg.com.
> a.udimg.com.
> fonts.googleapis.com.
> . . .
>
> Run with the 'while read $domain ; do echo ' pipe nothing appears
whatsoever.
> What am I doing wrong?
while read domain; do
     echo ${domain}
done < <(tcpdump -l -n -e port 53 | awk '{if ($14 ~ /A.*?/) print
$15}')

The "echo ${domain}" part is certainly just a simplification of a more
complex command to run on the variable. Else it would be pointless as 
awk is printing out the domain field 15.

Alexander

Tony Schreiner

2014-Dec-02 19:47 UTC

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[CentOS] Help with at Bash script

On Tue, Dec 2, 2014 at 2:19 PM, Alexander Dalloz <ad+lists at uni-x.org>
wrote:
> Am 02.12.2014 um 19:05 schrieb James B. Byrne:
>
>> I am attempting to get a script borrowed from DJB to work on my
CentOS-6.6
>> box.  Simplified it looks like this:
>>
>> tcpdump -l -n -e port 53 \
>>    | awk '{if ($14 ~ /A.*?/) print $15}' \
>>    | while read domain ; do echo $domain ; done ;
>>
>> The sticking point is the 'while read' construct.  Run just as
'tcpdum |
>> awk'
>> I get this:
>>
>> english.stackexchange.com.
>> www.urbandictionary.com.
>> www.urbandictionary.com.
>> www.urbandictionary.com.
>> www.urbandictionary.com.
>> api.mywot.com.
>> a.udimg.com.
>> a.udimg.com.
>> fonts.googleapis.com.
>> . . .
>>
>> Run with the 'while read $domain ; do echo ' pipe nothing
appears
>> whatsoever.
>> What am I doing wrong?
>>
>
> while read domain; do
>     echo ${domain}
> done < <(tcpdump -l -n -e port 53 | awk '{if ($14 ~ /A.*?/) print
$15}')
>
> The "echo ${domain}" part is certainly just a simplification of a
more
> complex command to run on the variable. Else it would be pointless as awk
> is printing out the domain field 15.
>
> Alexander
>

If not a typo in the message, your mistake, and I do it all the time, is
using

while read $domain

instead of

while read domain

Tony

Les Mikesell

2014-Dec-02 20:27 UTC

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[CentOS] Help with at Bash script

On Tue, Dec 2, 2014 at 1:19 PM, Alexander Dalloz <ad+lists at uni-x.org>
wrote:> Am 02.12.2014 um 19:05 schrieb James B. Byrne:
>>
>> I am attempting to get a script borrowed from DJB to work on my
CentOS-6.6
>> box.  Simplified it looks like this:
>>
>> tcpdump -l -n -e port 53 \
>>    | awk '{if ($14 ~ /A.*?/) print $15}' \
>>    | while read domain ; do echo $domain ; done ;
>>
>> The sticking point is the 'while read' construct.  Run just as
'tcpdum |
>> awk'
>> I get this:
>>
>> english.stackexchange.com.
>> www.urbandictionary.com.
>> www.urbandictionary.com.
>> www.urbandictionary.com.
>> www.urbandictionary.com.
>> api.mywot.com.
>> a.udimg.com.
>> a.udimg.com.
>> fonts.googleapis.com.
>> . . .
>>
>> Run with the 'while read $domain ; do echo ' pipe nothing
appears
>> whatsoever.
>> What am I doing wrong?
Works for me as is.  You just have to wait for your pipe buffer to
fill so the output is bursty.

-- 
   Les Mikesell
     lesmikesell at gmail.com

Hal Wigoda

2014-Dec-03 04:28 UTC

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[CentOS] Help with at Bash script

You have to do 
     cat domain 
in back tiks 

instead of read domain.    

(Sent from iPhone, so please accept my apologies in advance for any spelling or
grammatical errors.)
> On Dec 2, 2014, at 12:05 PM, James B. Byrne <byrnejb at
harte-lyne.ca> wrote:
> 
> I am attempting to get a script borrowed from DJB to work on my CentOS-6.6
> box.  Simplified it looks like this:
> 
> tcpdump -l -n -e port 53 \
>  | awk '{if ($14 ~ /A.*?/) print $15}' \
>  | while read domain ; do echo $domain ; done ;
> 
> The sticking point is the 'while read' construct.  Run just as
'tcpdum | awk'
> I get this:
> 
> english.stackexchange.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> api.mywot.com.
> a.udimg.com.
> a.udimg.com.
> fonts.googleapis.com.
> . . .
> 
> Run with the 'while read $domain ; do echo ' pipe nothing appears
whatsoever.
> What am I doing wrong?
> 
> -- 
> ***          E-Mail is NOT a SECURE channel          ***
> James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
> Harte & Lyne Limited          http://www.harte-lyne.ca
> 9 Brockley Drive              vox: +1 905 561 1241
> Hamilton, Ontario             fax: +1 905 561 0757
> Canada  L8E 3C3
> 
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos

Hal Wigoda

2014-Dec-03 04:29 UTC

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[CentOS] Help with at Bash script

What is domain, BTW?

(Sent from iPhone, so please accept my apologies in advance for any spelling or
grammatical errors.)
> On Dec 2, 2014, at 12:05 PM, James B. Byrne <byrnejb at
harte-lyne.ca> wrote:
> 
> I am attempting to get a script borrowed from DJB to work on my CentOS-6.6
> box.  Simplified it looks like this:
> 
> tcpdump -l -n -e port 53 \
>  | awk '{if ($14 ~ /A.*?/) print $15}' \
>  | while read domain ; do echo $domain ; done ;
> 
> The sticking point is the 'while read' construct.  Run just as
'tcpdum | awk'
> I get this:
> 
> english.stackexchange.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> www.urbandictionary.com.
> api.mywot.com.
> a.udimg.com.
> a.udimg.com.
> fonts.googleapis.com.
> . . .
> 
> Run with the 'while read $domain ; do echo ' pipe nothing appears
whatsoever.
> What am I doing wrong?
> 
> -- 
> ***          E-Mail is NOT a SECURE channel          ***
> James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
> Harte & Lyne Limited          http://www.harte-lyne.ca
> 9 Brockley Drive              vox: +1 905 561 1241
> Hamilton, Ontario             fax: +1 905 561 0757
> Canada  L8E 3C3
> 
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos

Keith Keller

2014-Dec-03 05:07 UTC

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[CentOS] Help with at Bash script

On 2014-12-03, Hal Wigoda <hal.wigoda at gmail.com>
wrote:> You have to do 
>      cat domain 
> in back tiks 
>
> instead of read domain.    
This is an error you can't blame on your device.  domain is not a file,
but a bash variable.  read takes stdin (which is what the OP's snippet
is doing) and populates the named variable(s) (domain in this case).

--keith


-- 
kkeller at wombat.san-francisco.ca.us

Alikhan Damirov

2014-Dec-03 13:20 UTC

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[CentOS] Help with at Bash script

if i understood cerrectly,you need that:
domain=$(tcpdump -l -n -e port 53 | awk '{if ($14 ~ /A.*?/) print $15}')
while read line
do echo $line
done < $domain

On 3 December 2014 at 08:29, Hal Wigoda <hal.wigoda at gmail.com> wrote:
> What is domain, BTW?
>
> (Sent from iPhone, so please accept my apologies in advance for any
> spelling or grammatical errors.)
>
> > On Dec 2, 2014, at 12:05 PM, James B. Byrne <byrnejb at
harte-lyne.ca>
> wrote:
> >
> > I am attempting to get a script borrowed from DJB to work on my
> CentOS-6.6
> > box.  Simplified it looks like this:
> >
> > tcpdump -l -n -e port 53 \
> >  | awk '{if ($14 ~ /A.*?/) print $15}' \
> >  | while read domain ; do echo $domain ; done ;
> >
> > The sticking point is the 'while read' construct.  Run just as
'tcpdum |
> awk'
> > I get this:
> >
> > english.stackexchange.com.
> > www.urbandictionary.com.
> > www.urbandictionary.com.
> > www.urbandictionary.com.
> > www.urbandictionary.com.
> > api.mywot.com.
> > a.udimg.com.
> > a.udimg.com.
> > fonts.googleapis.com.
> > . . .
> >
> > Run with the 'while read $domain ; do echo ' pipe nothing
appears
> whatsoever.
> > What am I doing wrong?
> >
> > --
> > ***          E-Mail is NOT a SECURE channel          ***
> > James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
> > Harte & Lyne Limited          http://www.harte-lyne.ca
> > 9 Brockley Drive              vox: +1 905 561 1241
> > Hamilton, Ontario             fax: +1 905 561 0757
> > Canada  L8E 3C3
> >
> > _______________________________________________
> > CentOS mailing list
> > CentOS at centos.org
> > http://lists.centos.org/mailman/listinfo/centos
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
>

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