The property replacer is a core component in rsyslogd's output system. A syslog message has a number of well-defined properties (see below). Each of this properties can be accessed and manipulated by the property replacer. With it, it is easy to use only part of a property value or manipulate the value, e.g. by converting all characters to lower case.
Syslog message properties are used inside templates. They are accessed by putting them between percent signs. Properties can be modified by the property replacer. The full syntax is as follows:
%propname:fromChar:toChar:options%propname is the
name of the property to access. It is case-insensitive (prior to 3.17.0, they were case-senstive).
Currently supported are:
| msg | the MSG part of the message (aka "the message" ;)) |
| rawmsg | the message excactly as it was received from the socket. Should be useful for debugging. |
| uxtradmsg | will disappear soon - do NOT use! |
| hostname | hostname from the message |
| source | alias for HOSTNAME |
| fromhost | hostname of the system the message was received from (in a relay chain, this is the system immediately in front of us and not necessarily the original sender) |
| syslogtag | TAG from the message |
| programname | the "static" part of the tag, as defined by BSD syslogd. For example, when TAG is "named[12345]", programname is "named". |
| pri | PRI part of the message - undecoded (single value) |
| pri-text | the PRI part of the message in a textual form (e.g. "syslog.info") |
| iut | the monitorware InfoUnitType - used when talking to a MonitorWare backend (also for phpLogCon) |
| syslogfacility | the facility from the message - in numerical form |
| syslogfacility-text | the facility from the message - in text form |
| syslogseverity | severity from the message - in numerical form |
| syslogseverity-text | severity from the message - in text form |
| syslogpriority | an alias for syslogseverity - included for historical reasons (be careful: it still is the severity, not PRI!) |
| syslogpriority-text | an alias for syslogseverity-text |
| timegenerated | timestamp when the message was RECEIVED. Always in high resolution |
| timereported | timestamp from the message. Resolution depends on what was provided in the message (in most cases, only seconds) |
| timestamp | alias for timereported |
| protocol-version | The contents of the PROTCOL-VERSION field from IETF draft draft-ietf-syslog-protcol |
| structured-data | The contents of the STRUCTURED-DATA field from IETF draft draft-ietf-syslog-protocol |
| app-name | The contents of the APP-NAME field from IETF draft draft-ietf-syslog-protocol |
| procid | The contents of the PROCID field from IETF draft draft-ietf-syslog-protocol |
| msgid | The contents of the MSGID field from IETF draft draft-ietf-syslog-protocol |
| $now | The current date stamp in the format YYYY-MM-DD |
| $year | The current year (4-digit) |
| $month | The current month (2-digit) |
| $day | The current day of the month (2-digit) |
| $hour | The current hour in military (24 hour) time (2-digit) |
| $hhour | The current half hour we are in. From minute 0 to 29, this is always 0 while from 30 to 59 it is always 1. |
| $qhour | The current quarter hour we are in. Much like $HHOUR, but values range from 0 to 3 (for the four quater hours that are in each hour) |
| $minute | The current minute (2-digit) |
Properties starting with a $-sign are so-called system properties. These do NOT stem from the message but are rather internally-generated.
FromChar and toChar
are used to build substrings. They specify the offset within the string
that should be copied. Offset counting starts at 1, so if you need to
obtain the first 2 characters of the message text, you can use this
syntax: "%msg:1:2%". If you do not whish to specify from and to, but
you want to specify options, you still need to include the colons. For
example, if you would like to convert the full message text to lower
case, use "%msg:::lowercase%". If you would like to extract from a
position until the end of the string, you can place a dollar-sign ("$")
in toChar (e.g. %msg:10:$%, which will extract from position 10 to the
end of the string).
There is also support for regular expressions.
To use them, you need to place a "R" into FromChar. This tells rsyslog
that a regular expression instead of position-based extraction is
desired. The actual regular expression must then be provided in toChar.
The regular expression must be followed by the
string "--end". It denotes the end of the regular expression and will
not become part of it. If you are using regular expressions, the
property replacer will return the part of the property text that
matches the regular expression. An example for a property replacer
sequence with a regular expression is: "%msg:R:.*Sev:. \(.*\)
\[.*--end%"
Also, extraction can be done based on so-called "fields". To do so, place a "F" into FromChar. A field in its current definition is anything that is delimited by a delimiter character. The delimiter by default is TAB (US-ASCII value 9). However, if can be changed to any other US-ASCII character by specifying a comma and the decimal US-ASCII value of the delimiter immediately after the "F". For example, to use comma (",") as a delimiter, use this field specifier: "F,44". If your syslog data is delimited, this is a quicker way to extract than via regular expressions (actually, a *much* quicker way). Field counting starts at 1. Field zero is accepted, but will always lead to a "field not found" error. The same happens if a field number higher than the number of fields in the property is requested. The field number must be placed in the "ToChar" parameter. An example where the 3rd field (delimited by TAB) from the msg property is extracted is as follows: "%msg:F:3%". The same example with semicolon as delimiter is "%msg:F,59:3%".
Please note that the special characters "F" and "R" are
case-sensitive. Only upper case works, lower case will return an error.
There are no white spaces permitted inside the sequence (that will lead
to error messages and will NOT provide the intended result).
property options are
case-insensitive. Currently, the following options are defined:
| uppercase | convert property to lowercase only |
| lowercase | convert property text to uppercase only |
| drop-last-lf | The last LF in the message (if any), is dropped. Especially useful for PIX. |
| date-mysql | format as mysql date |
| date-rfc3164 | format as RFC 3164 date |
| date-rfc3339 | format as RFC 3339 date |
| escape-cc | replace control characters (ASCII value 127 and values
less then 32) with an escape sequence. The sequnce is
"#<charval>" where charval is the 3-digit decimal value
of the control character. For example, a tabulator would be replaced by
"#009". Note: using this option requires that $EscapeControlCharactersOnReceive is set to off. |
| space-cc | replace control characters by spaces Note: using this option requires that $EscapeControlCharactersOnReceive is set to off. |
| drop-cc | drop control characters - the resulting string will
neither contain control characters, escape sequences nor any other
replacement character like space. Note: using this option requires that $EscapeControlCharactersOnReceive is set to off. |