# Control Structures

Control structures in RainerScript are similar in semantics to a lot of other mainstream languages such as C, Java, Javascript, Ruby, Bash etc. So this section assumes the reader is familier with semantics of such structures, and goes about describing RainerScript implementation in usage-example form rather than by formal-definition and detailed semantics documentation.

RainerScript supports following control structures:

if:

    if ($msg contains "important") then {
       if ( $. foo != "" ) then set $.foo = $.bar & $.baz;
       action(type="omfile" file="/var/log/important.log" template="outfmt")
    }

if/else-if/else:

    if ($msg contains "important") then {
       set $.foo = $.bar & $.baz;
       action(type="omfile" file="/var/log/important.log" template="outfmt")
    } else if ($msg startswith "slow-query:") then {
       action(type="omfile" file="/var/log/slow_log.log" template="outfmt")
    } else {
       set $.foo = $.quux;
       action(type="omfile" file="/var/log/general.log" template="outfmt")
    }

foreach:

    foreach ($.quux in $!foo) do {
       action(type="omfile" file="./rsyslog.out.log" template="quux")
       foreach ($.corge in $.quux!bar) do {
          reset $.grault = $.corge;
          action(type="omfile" file="./rsyslog.out.log" template="grault")
          if ($.garply != "") then
              set $.garply = $.garply & ", ";
          reset $.garply = $.garply & $.grault!baz;
       }
    }

Please note that asynchronous-action calls in foreach-statement body should almost always set action.copyMsg to on. This is because action calls within foreach usually want to work with the variable loop populates(in the above example, $.quux and $.corge) which causes message-mutation and async-action must see message as it was in a certain invocation of loop-body, so they must make a copy to keep it safe from further modification as iteration continues. For instance, an async-action invocation with linked-list based queue would look like:

    foreach ($.quux in $!foo) do {
       action(type="omfile" file="./rsyslog.out.log" template="quux" queue.type="linkedlist" action.copyMsg="on")
    }

call: The rsyslog “call” statement

continue: a NOP, useful e.g. inside the then part of an if