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Top Forums UNIX for Dummies Questions & Answers Shell script for search and replace by field Post 302732455 by Don Cragun on Saturday 17th of November 2012 07:17:07 PM
Old 11-17-2012
Quote:
Originally Posted by chandrath
Don,
Appreciate all your help!
Is there a way to improve performance of this script? Currently it's taking 1hr to process 200,000 source records with around 1000 records in rules file.

Thank you!
There are lots of ways to improve the performance of this script. Most of them involve reducing the tremendous flexibility that this script provides.
  1. Have different rules files for different input files. Use field numbers instead of field names in the rules files (getting rid of a level of indirection in every rule processed on every input line). Don't have rules in your rules file for fields that don't exist in your input file (every rule has to be evaluated for every line even if the rule can never match since it may apply in a later input file). Use a single character to indicate Equals and contains (less data to process and faster comparisons).
  2. Restrict the set of characters that appear in (or can be matched and replaced in rules). You could then use regular characters instead of character class expressions which might evaluate faster.
  3. Comment out or remove the debugging stuff from the script. (But only do this after you have finished changing the script forever and you are sure how it works.) Better would be to keep the debugging stuff in your source script, but strip out the debugging tests in a version you use for production runs.
  4. Get rid of the reject file and just log errors instead of logging all changes.
  5. Rewrite it in C (or some other language that is compiled rather than interpreted).
 

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AUSEARCH_ADD_ITEM(3)						  Linux Audit API					      AUSEARCH_ADD_ITEM(3)

NAME
ausearch_add_item - build up search rule SYNOPSIS
#include <auparse.h> int ausearch_add_item(auparse_state_t *au, const char *field, const char *op, const char *value, ausearch_rule_t how); DESCRIPTION
ausearch_add_item adds one search condition to the current audit search expression. The search conditions can then be used to scan logs, files, or buffers for something of interest. The field value is the field name that the value will be checked for. The op variable describes what kind of check is to be done. Legal op values are: exists just check that a field name exists = locate the field name and check that the value associated with it is equal to the value given in this rule. != locate the field name and check that the value associated with it is NOT equal to the value given in this rule. The value parameter is compared to the uninterpreted field value. The how value determines how this search condition will affect the existing search expression if one is already defined. The possible val- ues are: AUSEARCH_RULE_CLEAR Clear the current search expression, if any, and use only this search condition. AUSEARCH_RULE_OR If a search expression E is already configured, replace it by (E || this_search_condition). AUSEARCH_RULE_AND If a search expression E is already configured, replace it by (E && this_search_condition). RETURN VALUE
Returns -1 if an error occurs; otherwise, 0 for success. SEE ALSO
ausearch_add_expression(3), ausearch_add_interpreted_item(3), ausearch_add_timestamp_item(3), ausearch_add_regex(3), ausearch_set_stop(3), ausearch_clear(3), ausearch_next_event(3), ausearch-expression(5). AUTHOR
Steve Grubb Red Hat Nov 2007 AUSEARCH_ADD_ITEM(3)
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