Piping the output of a tail | grep command into a text file

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DeadTOm76
Posts: 44
Joined: 2017-09-22 15:36
Location: Missoula, MT USA

Piping the output of a tail | grep command into a text file

#1 Post by DeadTOm76 »

My phone is occasionally having some trouble on my home network, and I'm trying to get a feel for what's happening as it goes in and out of my firewall.

I can run this command and watch the traffic in real time:

Code: Select all

tail -f /var/log/syslog | grep "<phone-ip>"
What I want to do is pipe that into a text file so that I can let it go for a few hours, and go over it later.

This is the command I'm running:

Code: Select all

tail -f /var/log/syslog | grep "<phone-ip>" > phone.log
I'm clearly doing something wrong though, because all this produces is a blank phone.log.

Any idea what I'm doing wrong here?

Thanks!

cronoik
Posts: 310
Joined: 2015-05-20 21:17

Re: Piping the output of a tail | grep command into a text f

#2 Post by cronoik »

You need buffering [1]:

Code: Select all

tail -f /var/log/syslog | grep --line-buffered "<phone-ip>" > phone.log
[1] http://mywiki.wooledge.org/BashFAQ/009
Have a nice day!

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DeadTOm76
Posts: 44
Joined: 2017-09-22 15:36
Location: Missoula, MT USA

Re: Piping the output of a tail | grep command into a text f

#3 Post by DeadTOm76 »

cronoik wrote:You need buffering [1]:

Code: Select all

tail -f /var/log/syslog | grep --line-buffered "<phone-ip>" > phone.log
[1] http://mywiki.wooledge.org/BashFAQ/009

Yup, that did it. Thanks!

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dilberts_left_nut
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Joined: 2009-10-05 07:54
Location: enzed

Re: Piping the output of a tail | grep command into a text f

#4 Post by dilberts_left_nut »

Or you could just ‘grep phoneip /var/log/syslog’ at the end of your test period.
AdrianTM wrote:There's no hacker in my grandma...

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