how to grep(1) loop output

m4rtin · 03-24-2011, 11:58 AM

I have a following endless loop checking for lost packets:

Code:

while [ 1 = 1 ]; do ping -f -i1 -c1 192.168.1.1 | while read i; do echo "$(date "+%T %d.%m"): $i" ;done ;done | grep "\: \."

..which generates following output:

Code:

:~> while [ 1 = 1 ]; do ping -i1 -f -c1 192.168.1.1 | while read i; do echo "$(date "+%T %d.%m"): $i"; done; done | grep '\: \.'
18:50:00 24.03:  
18:50:00 24.03:  
18:50:00 24.03:  
18:50:00 24.03:  
18:50:00 24.03:  
18:50:00 24.03:  
18:50:00 24.03:  
18:50:00 24.03:  
18:50:00 24.03:  
18:50:10 24.03: .
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:10 24.03:  
18:50:11 24.03:  
18:50:11 24.03:  
18:50:11 24.03:  
18:50:11 24.03:  
18:50:11 24.03:  
18:50:11 24.03:  
18:50:11 24.03:  
18:50:21 24.03: .
18:50:31 24.03: .
18:50:31 24.03:  
18:50:41 24.03: .
18:50:41 24.03:

However, there are few problems. How to stop this? I mean "Ctrl + c" does not work

And the main thing is, why does it print lines which do not contain ": ." pattern?

szboardstretcher · 03-24-2011, 12:04 PM

Quote:

Originally Posted by m4rtin

And the main thing is, why does it print lines which do not contain ": ." pattern?

echo "$(date "+%T %d.%m"): $i" is printing the date lines.

I guess you could do something like:

Code:

#!/bin/bash
while true;
do
 i=`ping -f -i1 -c1 192.168.1.1`
 d=$(date "+%T %d.%m")
 if [[ $i == *dropped* ]]
  then
  echo "$d: Packet Lost";
 fi
done;

I used the word 'dropped' because I'm not sure what exactly you were grepping for. But this will sit there with no output, until it sees the word "dropped" then it will display the time and Packet Lost like:

Code:

13:30:08 24.03: Packet Lost