Functions — rsyslog 8.24.0 documentation

# Functions

RainerScript supports a currently quite limited set of functions:

## getenv(str)

> like the OS call, returns the value of the environment variable, if it exists. Returns an empty string if it does not exist.

> The following example can be used to build a dynamic filter based on some environment variable:

    if $msg contains getenv('TRIGGERVAR') then /path/to/errfile

## strlen(str)

> returns the length of the provided string

## tolower(str)

> converts the provided string into lowercase

## cstr(expr)

> converts expr to a string value

## cnum(expr)

> converts expr to a number (integer) Note: if the expression does not contain a numerical value, behaviour is undefined.

## wrap(str, wrapper_str)

> returns the str wrapped with wrapper_str. Eg.

    wrap("foo bar", "##")

produces

    "##foo bar##"

## wrap(str, wrapper_str, escaper_str)

> returns the str wrapped with wrapper_str. But additionally, any instances of wrapper_str appearing in str would be replaced by the escaper_str. Eg.

    wrap("foo'bar", "'", "_")

produces

    "'foo_bar'"

## replace(str, substr_to_replace, replace_with)

> returns new string with all instances of substr_to_replace replaced by replace_with. Eg.

    replace("foo bar baz", " b", ", B")

produces

    "foo, Bar, Baz".

## re_match(expr, re)

> returns 1, if expr matches re, 0 otherwise. Uses POSIX ERE.

## re_extract(expr, re, match, submatch, no-found)

> extracts data from a string (property) via a regular expression match. POSIX ERE regular expressions are used. The variable “match” contains the number of the match to use. This permits to pick up more than the first expression match. Submatch is the submatch to match (max 50 supported). The “no-found” parameter specifies which string is to be returned in case when the regular expression is not found. Note that match and submatch start with zero. It currently is not possible to extract more than one submatch with a single call.

## field(str, delim, matchnbr)

> returns a field-based substring. str is the string to search, delim is the delimiter and matchnbr is the match to search for (the first match starts at 1). This works similar as the field based property-replacer option. Versions prior to 7.3.7 only support a single character as delimiter character. Starting with version 7.3.7, a full string can be used as delimiter. If a single character is being used as delimiter, delim is the numerical ascii value of the field delimiter character (so that non-printable characters can by specified). If a string is used as delmiter, a multi-character string (e.g. “#011”) is to be specified.

> Note that when a single character is specified as string `field($msg, ",", 3)` a string-based extraction is done, which is more performance intense than the equivalent single-character `field($msg, 44 ,3)` extraction. Eg.

    set $!usr!field = field($msg, 32, 3);  -- the third field, delimited by space

    set $!usr!field = field($msg, "#011", 2); -- the second field, delmited by "#011"

## prifilt(constant)

> mimics a traditional PRI-based filter (like “*.*” or “mail.info”). The traditional filter string must be given as a constant string. Dynamic string evaluation is not permitted (for performance reasons).

## dyn_inc(bucket_name_litteral_string, str)

> Increments counter identified by `str` in dyn-stats bucket identified by `bucket_name_litteral_string`. Returns 0 when increment is successful, any other return value indicates increment failed.

> Counters updated here are reported by impstats.

> Except for special circumstances (such as memory allocation failing etc), increment may fail due to metric-name cardinality being under-estimated. Bucket is configured to support a maximum cardinality (to prevent abuse) and it rejects increment-operation if it encounters a new(previously unseen) metric-name(`str`) when full.

> Read more about it here Dynamic Stats

## lookup(table_name_litteral_string, key)

> Lookup tables are a powerful construct to obtain class information based on message content. It works on top of a data-file which maps key (to be looked up) to value (the result of lookup).

> The idea is to use a message properties (or derivatives of it) as an index into a table which then returns another value. For example, $fromhost-ip could be used as an index, with the table value representing the type of server or the department or remote office it is located in.

> Read more about it here Lookup Tables