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Old 09-05-2014, 12:12 PM   #1
Gursharan
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Grep Command


Hello Pros

I kind of new to Linux and i was recently grepping the Cisco firewall logs on CentOS server, I was grepping on the timestamp which gave me undesired results

i was using the following command

grep 17:0 /boot/*

and i was getting the following output. I was looking to for logs starting from 17:00 hrs and not 00:17 0r 01:17

Sep 4 00:17:08 x.x.x.x.x %FWSM-6-302014

Sep 4 00:17:08 x.x.x.x.x %FWSM-6-302013

My question is how can i modify this grep command to get exact results for logs matching 17:00 hrs onwards.

Thanks
 
Old 09-05-2014, 12:26 PM   #2
keefaz
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Put a space before 17 ?
grep " 17:0" /boot/*
 
Old 09-05-2014, 12:30 PM   #3
Gursharan
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Thanks Keefaz

Why do i need to put double quotes around my query. Just trying to learm.
 
Old 09-05-2014, 12:34 PM   #4
ondoho
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Quote:
Originally Posted by Gursharan View Post
Just trying to learn.
so, instead of telling you why, i say:
the answer is already in you.
you tell me why, and then i will tell you if you're wrong or right.
 
Old 09-05-2014, 03:00 PM   #5
Gursharan
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Thank Ondoho.

Since we have included a space we don't want to search on file named 17:0 and other files (\boot\*) . We want to search the on entire string which is ( 17:0)

I am correct on this
 
Old 09-06-2014, 04:33 PM   #6
selfprogrammed
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Grep
Grep allows the unquoted string, but it is limited by what BASH will let pass.
Use quotes when you want to be exact, or anytime you are unsure.
You will still have problems with some characters that are specially interpreted.
Then you will have to backslash characters to get the search you want.

Example:
>> grep " 17:00" *
- without the quotes, the space would not be in the search string. This applies to arbitrary strings.

>> grep "The quick brown fox went up the twisty road" *

Example:
>> grep " fred[" *
- will not work, will get an error message

>> grep " fred\[" *
- backslashed to get the square bracket into the search string as it is.

Advanced:
>> grep " 17:00" * | grep " something else"
- to apply more than one grep test to a line

Try this:
>> grep " 1[789]:00" *
and look into rgrep and egrep.

Last edited by selfprogrammed; 09-06-2014 at 04:42 PM.
 
Old 09-06-2014, 07:00 PM   #7
ondoho
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Quote:
Originally Posted by Gursharan View Post
I am correct on this
hallelu - jah!
 
  


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