Pattern matching in file and then display 10 lines above every time Post: 302162944

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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

01-30-2008

Registered User

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)

drl

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shift

shift(1)                                                           User Commands                                                          shift(1)

NAME

       shift - shell built-in function to traverse either a shell's argument list or a list of field-separated words

SYNOPSIS

   sh
       shift [n]

   csh
       shift [variable]

   ksh
       * shift [n]

DESCRIPTION

   sh
       The positional parameters from $n+1 ... are renamed $1 ... . If n is not given, it is assumed to be 1.

   csh
       The  components of argv, or variable, if supplied, are shifted to the left, discarding the first component. It is an error for the variable
       not to be set or to have a null value.

   ksh
       The positional parameters from $n+1 $n+1 ... are renamed $1 ..., default n is 1. The parameter n can  be  any  arithmetic  expression  that
       evaluates to a non-negative number less than or equal to $#.

       On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

       1.  Variable assignment lists preceding the command remain in effect when the command completes.

       2.  I/O redirections are processed after variable assignments.

       3.  Errors cause a script that contains them to abort.

       4.  Words,  following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a vari-
           able assignment. This means that tilde substitution is performed after the = sign and word splitting and file name generation  are  not
           performed.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |SUNWcsu                      |
       +-----------------------------+-----------------------------+

SEE ALSO

       csh(1), ksh(1), sh(1), attributes(5)

SunOS 5.10                                                          15 Apr 1994                                                           shift(1)

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