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Full Discussion: Pattern matching in file and then display 10 lines above every time
Top Forums Shell Programming and Scripting Pattern matching in file and then display 10 lines above every time Post 302162944 by drl on Wednesday 30th of January 2008 07:24:54 PM
Old 01-30-2008
Hi.

If I understand the problem and the solution from ennstate, then sed will be loaded up 1000 times. Here is an alternate solution. The attachment is a perl script, pvg (perl version of grep, very limited edition). Assuming that you have perl, this will do simple matching and it will also do the "-B n" behavior of GNU grep. This can then be called once to process the log file. (Get the attachment, rename it to "pvg", then run the test script.) Execute "./pvg -h" for a help page.

Here's a test script:
Code:
#!/bin/bash -

# @(#) s3       Demonstrate printing of text before a matched line.

echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version =o $(_eat $0 $1)

P=./pvg

echo
echo " Input file data3:"
cat data3

echo
echo " Looking for d, normal search:"
$P d data3

echo
echo " Looking for d, print previous 2:"
$P -B 2 d data3

echo
echo " Looking for d, print previous 2, separator:"
$P -s '     ----- \n' -B 2 d data3

echo
echo " Looking for ask, print previous 100, quiet:"
$P -q -B 100 ask data3

exit 0

Producing:
Code:
% ./s3
(Versions displayed with local utility "version")
Linux 2.6.11-x1
GNU bash 2.05b.0

 Input file data3:
     1  Alabama AL
     2  Alaska AK
     3  Arizona AZ
     4  Arkansas AR
     5  California CA
     6  Colorado CO
     7  Connecticut CT
     8  Delaware DE
     9  District of Columbia DC
    10  Florida FL

 Looking for d, normal search:
     6  Colorado CO
    10  Florida FL
 ( Lines read: 10; hits: 2 )

 Looking for d, print previous 2:
     4  Arkansas AR
     5  California CA
     6  Colorado CO
     8  Delaware DE
     9  District of Columbia DC
    10  Florida FL
 ( Lines read: 10; hits: 2 )

 Looking for d, print previous 2, separator:
     4  Arkansas AR
     5  California CA
     6  Colorado CO
     -----
     8  Delaware DE
     9  District of Columbia DC
    10  Florida FL
 ( Lines read: 10; hits: 2 )

 Looking for ask, print previous 100, quiet:
     1  Alabama AL
     2  Alaska AK

It can be a lot of work to make sure that perl and friends are installed, but once it's done, then you can use it for many things. Most systems have it already available.

There is also cgrep at freshmeat.net: Project details for cgrep which has a wealth of features. You need to go through a compilation, but it was fairly painless.

Best wishes ... cheers, drl
pvg.txt (3.5 KB) 
 

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LEARN ABOUT LINUX

shtool-echo

SHTOOL-ECHO.TMP(1)					      GNU Portable Shell Tool						SHTOOL-ECHO.TMP(1)

NAME

       shtool-echo - GNU shtool echo(1) extensional command

SYNOPSIS

       shtool echo [-n|--newline] [-e|--expand] string

DESCRIPTION

       shtool echo is an echo(1) style command which prints string to stdout and optionally provides special expansion constructs (terminal bold
       mode, environment details, date, etc) and newline control. The trick of this command is that it provides a portable -n option and hides the
       gory details needed to find out the environment details under option -e.

OPTIONS

       The following command line options are available.

       -n, --newline
	   By default, output is written to stdout followed by a "newline" (ASCII character 0x0a). If option -n is used, this newline character is
	   omitted.

       -e, --expand
	   If option -e is used, string can contain special "%x" constructs which are expanded before the output is written. Currently the
	   following constructs are recognized:

	   %B  switch terminal mode to bold display mode.

	   %b  switch terminal mode back to normal display mode.

	   %u  the current user name.

	   %U  the current user id (numerical).

	   %g  the current group name.

	   %G  the current group id (numerical).

	   %h  the current hostname (without any domain extension).

	   %d  the current domain name.

	   %D  the current day of the month.

	   %M  the current month (numerical).

	   %m  the current month name.

	   %Y  the current year.

EXAMPLE

	#   shell script
	shtool echo -n -e "Enter your name [%B%u%b]: "; read name
	shtool echo -e "Your Email address might be %u@%h%d"
	shtool echo -e "The current date is %D-%m-%Y"

HISTORY

       The GNU shtool echo command was originally written by Ralf S.  Engelschall <rse@engelschall.com> in 1998 for Website META Language (WML)
       under the name buildinfo. It was later taken over into GNU shtool.

SEE ALSO

       shtool(1), echo(1).

18-Jul-2008							   shtool 2.0.8 						SHTOOL-ECHO.TMP(1)
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