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# 1  
Old 03-31-2005
Large files

I am trying to understand the webserver log file for an error which has occured on my live web site.

The webserver access file is very big in size so it's not possible to open this file using vi editor. I know the approximate time the error occured, so i am interested in looking for the log file entries just before and just after that time (Each line in this log file contain time stamp).

Is there a easy way to get 50 lines before and 50 lines after this time stamp (from the middle of the file) and redirect that to a temporary file so that i can examine that using any windows editor if required.

Any help will be appreciated...

# 2  
Old 03-31-2005
This is still going to be slow, but nethertheless, if you're using GNU grep (please state if you're not, try "grep --version", if this displays an error, you're not using GNU grep), do something like the following....

grep -C 50 "my_timestamp_here" logfile > matched_lines

As I say, if you're not using GNU grep let us know which OS/shell you're using and we'll assist further.

# 3  
Old 03-31-2005
Thanks for the reply..

I am not using GNU grep. The server i am using : SunOS bart 5.8 Generic_108528-21 sun4u sparc SUNW,Ultra-4

Shell is : ksh

# 4  
Old 03-31-2005
There is no doubt a far quicker way of doing this (we're going through the file twice, so it'll take a while), but something like

matches=`grep -n "TIMESTAMP_HERE" logfile | cut -f1 -d:`
first_match=`echo "$matches" | awk 'NR==1{print $0}'`
last_match=`echo "$matches" | awk '{c=$0}END{print c}'`

sed -n "$((first_match - 50)),$((last_match + 50))p" logfile

Should do it - just redirect the output of this script to your temporary file

Tested on SunOS sunbox 5.9 Generic_112234-07 i86pc i386 i86pc, ksh


Last edited by zazzybob; 03-31-2005 at 07:59 AM.. Reason: Removed debug code
# 5  
Old 03-31-2005
Looks tricky,
Thanks a lot for your help

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