syslog-ng Open Source Edition 3.38 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng The syslog-ng OSE quick-start guide The syslog-ng OSE configuration file source: Read, receive, and collect log messages
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files wildcard-file: Collecting messages from multiple text files kubernetes: Collecting and parsing the Kubernetes CRI (Container Runtime Interface) format linux-audit: Collecting messages from Linux audit logs mqtt: receiving messages from an MQTT broker network: Collecting messages using the RFC3164 protocol (network() driver) nodejs: Receiving JSON messages from nodejs applications mbox: Converting local email messages to log messages osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes pacct: Collecting process accounting logs on Linux program: Receiving messages from external applications python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources snmptrap: Read Net-SNMP traps sun-streams: Collecting messages on Sun Solaris syslog: Collecting messages using the IETF syslog protocol (syslog() driver) system: Collecting the system-specific log messages of a platform systemd-journal: Collecting messages from the systemd-journal system log storage systemd-syslog: Collecting systemd messages using a socket tcp, tcp6, udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol— OBSOLETE unix-stream, unix-dgram: Collecting messages from UNIX domain sockets stdin: Collecting messages from the standard input stream
destination: Forward, send, and store log messages
amqp: Publishing messages using AMQP collectd: sending metrics to collectd discord: Sending alerts and notifications to Discord elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED) elasticsearch-http: Sending messages to Elasticsearch HTTP Bulk API file: Storing messages in plain-text files graphite: Sending metrics to Graphite Sending logs to Graylog hdfs: Storing messages on the Hadoop Distributed File System (HDFS) Posting messages over HTTP http: Posting messages over HTTP without Java kafka: Publishing messages to Apache Kafka (Java implementation) kafka-c(): Publishing messages to Apache Kafka using the librdkafka client (C implementation) loggly: Using Loggly logmatic: Using mongodb(): Storing messages in a MongoDB database mqtt() destination: sending messages from a local network to an MQTT broker network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) osquery: Sending log messages to osquery's syslog table pipe: Sending messages to named pipes program: Sending messages to external applications pseudofile() python: writing custom Python destinations redis: Storing name-value pairs in Redis riemann: Monitoring your data with Riemann slack: Sending alerts and notifications to a Slack channel smtp: Generating SMTP messages (email) from logs snmp: Sending SNMP traps Splunk: Sending log messages to Splunk sql: Storing messages in an SQL database stomp: Publishing messages using STOMP Sumo Logic destinations: sumologic-http() and sumologic-syslog() syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng(): Forward logs to another syslog-ng node tcp, tcp6, udp, udp6: Sending messages to a remote log server using the legacy BSD-syslog protocol (tcp(), udp() drivers) Telegram: Sending messages to Telegram unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal: usertty() destination Write your own custom destination in Java or Python Client-side failover
log: Filter and route log messages using log paths, flags, and filters Global options of syslog-ng OSE TLS-encrypted message transfer template and rewrite: Format, modify, and manipulate log messages parser: Parse and segment structured messages
Parsing syslog messages Parsing messages with comma-separated and similar values Parsing key=value pairs JSON parser XML parser Parsing dates and timestamps Python parser Parsing tags Apache access log parser Linux audit parser Cisco parser Parsing enterprise-wide message model (EWMM) messages iptables parser Netskope parser panos-parser(): parsing PAN-OS log messages Sudo parser MariaDB parser Websense parser Fortigate parser Check Point Log Exporter parser Regular expression (regexp) parser db-parser: Process message content with a pattern database (patterndb)
Correlating log messages Enriching log messages with external data Statistics of syslog-ng Multithreading and scaling in syslog-ng OSE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages Creative Commons Attribution Non-commercial No Derivatives (by-nc-nd) License The syslog-ng Open Source Edition Documentation License Glossary

Options of regular expressions

This chapter lists regular expressions supported by syslog-ng Open Source Edition (syslog-ng OSE) and their available supported type() and flags() options.

By default, syslog-ng OSE uses PCRE-style regular expressions. To use other expression types, add the type() option after the regular expression.

The syslog-ng OSE application supports the following regular expression type() options:

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The type() options of regular expressions

By default, syslog-ng OSE uses PCRE-style regular expressions, which are supported on every platform starting with syslog-ng OSE version 3.1. To use other expression types, add the type() option after the regular expression.

The syslog-ng OSE application supports the following type() options:

Perl Compatible Regular Expressions (pcre)

Description: Uses Perl Compatible Regular Expressions (PCRE). If the type() parameter is not specified, syslog-ng OSE uses PCRE regular expressions by default.

For more information about the flags() options of PCRE regular expressions, see The flags() options of regular expressions.

Literal string searches (string)

Description: Matches the strings literally, without regular expression support. By default, only identical strings are matched. For partial matches, use the flags("prefix") or the flags("substring") flags.

For more information about the flags() options of literal string searches, see The flags() options of regular expressions.

Glob patterns without regular expression support (glob)

Description: Matches the strings against a pattern containing * and ? wildcards, without regular expression and character range support. The advantage of glob patterns to regular expressions is that globs can be processed much faster.

  • *: matches an arbitrary string, including an empty string

  • ?: matches an arbitrary character

  • The wildcards can match the / character.

  • You cannot use the * and ? literally in the pattern.

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The flags() options of regular expressions

Similarly to the type() options, the flags() options are also optional within regular expressions.

The following list describes each type() option's flags() options.


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Perl Compatible Regular Expressions (PCRE)

Starting with syslog-ng OSE version 3.1, PCRE expressions are supported on every platform. If the type() parameter is not specified, syslog-ng OSE uses PCRE regular expressions by default.

The following example shows the structure of PCRE-style regular expressions in use.

Example: Using PCRE regular expressions
rewrite r_rewrite_subst {
    subst("a*", "?", value("MESSAGE") flags("utf8" "global"));  

PCRE-style regular expressions have the following flags() options:


Allows using duplicate names for named subpatterns.

Configuration example:

filter { match("(?<DN>foo)|(?<DN>bar)" value(MSG) flags(store-matches, dupnames)); };
destination { file(/dev/stdout template("$DN\n")); };

Usable only in rewrite rules, flags("global") matches for every occurrence of the expression, not only the first one.


Disables case-sensitivity.


When configured, it changes the newline definition used in PCRE regular expressions to accept either of the following:

  • a single carriage-return
  • linefeed
  • the sequence carriage-return and linefeed (\r, \n and \r\n, respectively)

This newline definition is used when the circumflex and dollar patterns (^ and $) are matched against an input. By default, PCRE interprets the linefeed character as indicating the end of a line. It does not affect the \r, \n or \R characters used in patterns.


Stores the matches of the regular expression into the $0, ... $255 variables. The $0 stores the entire match, $1 is the first group of the match (parentheses), and so on. Named matches (also called named subpatterns), for example, (?<name>...), are stored as well. Matches from the last filter expression can be referenced in regular expressions.

NOTE: To convert match variables into a syslog-ng OSE list, use the $* macro, which can be further manipulated using List manipulation, or turned into a list in type-aware destinations.


Uses Unicode support for UTF-8 matches: UTF-8 character sequences are handled as single characters.


An alias for the unicode flag.

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