ausearch-expression − audit search expression format
This man page describes the format of "ausearch expressions". Parsing and evaluation of these expressions is provided by libauparse and is common to applications that use this library.
(ASCII space, tab and new-line characters) between tokens is
ignored. The following tokens are recognized:
( ) \
! && ||
< <= == > >= !== i= i!= r= r!=
Any non-empty sequence of ASCII letters, digits, and the _ symbol.
A sequence of characters surrounded by the " quotes. The \ character starts an escape sequence. The only defined escape sequences are \\ and \". The semantics of other escape sequences is undefined.
A sequence of characters surrounded by the / characters. The \ character starts an escape sequence. The only defined escape sequences are \\ and \/. The semantics of other escape sequences is undefined.
Anywhere an unquoted string is valid, a quoted string is valid as well, and vice versa. In particular, field names may be specified using quoted strings, and field values may be specified using unquoted strings.
The primary expression has one of the following forms:
field comparison-operator value
field is either a string, which specifies the first field with that name within the current audit record, or the \ escape character followed by a string, which specifies a virtual field with the specified name (virtual fields are defined in a later section).
field is a string. operator specifies the comparison to perform
Get the "raw" string of field, and compare it to value. For fields in audit records, the "raw" string is the exact string stored in the audit record (with all escaping and unprintable character encoding left alone); applications can read the "raw" string using auparse_get_field_str(3). Each virtual field may define a "raw" string. If field is not present or does not define a "raw" string, the result of the comparison is false (regardless of the operator).
Get the "interpreted" string of field, and compare it to value. For fields in audit records, the "interpreted" string is an "user-readable" interpretation of the field value; applications can read the "interpreted" string using auparse_interpret_field(3). Each virtual field may define an "interpreted" string. If field is not present or does not define an "interpreted" string, the result of the comparison is false (regardless of the operator).
< <= == > >= !==
Evaluate the "value" of field, and compare it to value. A "value" may be defined for any field or virtual field, but no "value" is currently defined for any audit record field. The rules of parsing value for comparing it with the "value" of field are specific for each field. If field is not present, the result of the comparison is false (regardless of the operator). If field does not define a "value", an error is reported when parsing the expression.
In the special case of \regexp regexp-or-string, the current audit record is taken as a string (without interpreting field values), and matched against regexp-or-string. regexp-or-string is an extended regular expression, using a string or regexp token (in other words, delimited by " or /).
If E1 and E2 are valid expressions, then ! E1, E1 && E2, and E1 || E2 are valid expressions as well, with the usual C semantics and evaluation priorities. Note that ! field op value is interpreted as !(field op value), not as (!field) op value.
virtual fields are defined:
The value is the timestamp of the current event. value must have the ts:seconds.milli format, where seconds and milli are decimal numbers specifying the seconds and milliseconds part of the timestamp, respectively.
The value is the type of the current record. value is either the record type name, or a decimal number specifying the type.
The expression as a whole applies to a single record. The expression is true for a specified event if it is true for any record associated with the event.
As a demonstration of the semantics of handling missing fields, the following expression is true if field is present:
(field r= "") || (field r!= "")
and the same expression surrounded by !( and ) is true if field is not present.
New escape sequences for quoted strings may be defined.
For currently defined virtual fields that do not define a "raw" or "interpreted" string, the definition may be added. Therefore, don’t rely on the fact that comparing the "raw" or "interpreted" string of the field with any value is false.
New formats of value constants for the \timestamp virtual field may be added.
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.