Would like to print 3 lines after a regular expression is found in the logfile

Shell Programming and Scripting
1

I would like to print 3 lines after a regular expression is found in the logfile. I'm using the following code:

grep -n "$reg_exp" file.txt |while read LINE ;do i=$(echo $LINE |cut -d':' -f1 ) ;sed -n "$i,$(($i+3))p" file.txt ;done

The above code things works fine,but sometimes gives erroneous results. In my case i'm searching for the expression X104 in the logfile. Sometimes X104 will contain only 1 line to print and after printing that .It also prints the next 3 lines after that, e.g:

(i)11/02/09 02:21:15 X104
Text : Unable to unlink/erase file
System Error Number: 13 (d) - The data is invalid.

(ii) Text : X104 disabled.

(iii) 11/03/09 01:01:03 web200
Text : Freespace on C: is at a critical level (694.55MB).
Text : X104 enabled per scheduled_reboot.
NSLOOKUP was successful. Please reload your
configuration.

(i) : I get the desired results, regexp is found and the next 3 lines are printed
(ii) : regexp is matched (contains only 1 line) and printed, but I receive the next 3 lines (including the newline) which I find not useful for me.

Can anyone help me out

2

GNU grep:

grep -A3
3

I'm using Solaris 8 and that option is not available with grep

4

Hi,

Test next 'perl' command:

$ perl -ne 'BEGIN { $lines_to_print = 3; $regexp = "X104"; $i = 1 } do { print unless /^\s*$/ ; ++$i ; next } if ( /(?i:$regexp)/ .. ( /^\s*$/ || $i >= $lines_to_print ) ) ; $i = 1' infile
(i)11/02/09 02:21:15 X104
Text : Unable to unlink/erase file
System Error Number: 13 (d) - The data is invalid.
(ii) Text : X104 disabled.
Text : X104 enabled per scheduled_reboot.
NSLOOKUP was successful. Please reload your

Regards,
Birei