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<h1>RainerScript ABNF</h1>
This is the formal definition of RainerScript, as supported by
rsyslog configuration. Please note that this currently is working
document and the actual implementation may be quite different.
The
first glimpse of RainerScript will be available as part of rsyslog
3.12.0 expression support. However, the 3.12. series of rsyslog will
have a partial script implementaiton, which will not necessariy be
compatible with the later full implementation. So if you use it, be
prepared for some config file changes as RainerScript evolves.
C-like comments (/* some comment */) are supported in all pure
RainerScript lines. However, legacy-mapped lines do not support them.
All lines support the hash mark "#" as a comment initiator. Everything
between the hash and the end of line is a comment (just like // in C++
and many other languages).
<h2>Formal Definition</h2>
Below is the formal language definitionin ABNF (RFC 2234)
format: 

<pre>; all of this is a working document and may change! -- rgerhards, 2008-02-24 script := *stmt stmt := (if_stmt / block / vardef / run_s / load_s) vardef := "var" ["scope" = ("global" / "event")] block := "begin" stmt "end" load_s := "load" constraint ("module") modpath params ; load mod only if expr is true run_s := "run" constraint ("input") name constraint:= "if" expr ; constrains some one-time commands modpath := expr params := ["params" *1param *("," param) "endparams"] param := paramname) "=" expr paramname := [*(obqualifier ".") name] modpath:= ; path to module ?line? := cfsysline / cfli cfsysline:= BOL "$" *char EOL ; how to handle the first line? (no EOL in front!) BOL := ; Begin of Line - implicitely set on file beginning and after each EOL EOL := 0x0a ;LF if_stmt := "if" expr "then" old_filter:= BOL facility "." severity ; no whitespace allowed between BOL and facility! facility := "*" / "auth" / "authpriv" / "cron" / "daemon" / "kern" / "lpr" / "mail" / "mark" / "news" / "security" / "syslog" / "user" / "uucp" / "local0" .. "local7" / "mark" 	; The keyword security should not be used anymore 	; mark is just internal severity := TBD ; not really relevant in this context ; and now the actual expression expr := e_and *("or" e_and) e_and := e_cmp *("and" e_cmp) e_cmp := val 0*1(cmp_op val) val := term *(("+" / "-" / "&amp;") term) term := factor *(("*" / "/" / "%") factor) factor := ["not"] ["-"] terminal terminal := var / constant / function / ( "(" expr ")" ) function := name "(" *("," expr) ")" var := "$" varname varname := msgvar / sysvar msgvar := name sysvar := "$" name name := alpha *(alnum) constant := string / number string := simpstr / tplstr ; tplstr will be implemented in next phase simpstr := "'" *char "'" ; use your imagination for char ;) tplstr := '"' template '"' ; not initially implemented number := ["-"] 1*digit ; 0nn = octal, 0xnn = hex, nn = decimal cmp_op := "==" / "!=" / "&lt;&gt;" / "&lt;" / "&gt;" / "&lt;=" / "&gt;=" / "contains" / "contains_i" / "startswith" / "startswith_i" digit := %x30-39 alpha := "a" ... "z" # all letters alnum :* alpha / digit / "_" /"-" # "-" necessary to cover currently-existing message properties </pre>
<h2>Samples</h2>
Some samples of RainerScript:define function IsLinux begin &nbsp; &nbsp; if $environ contains "linux" then return true else return false endload if IsLinux() 'imklog.so' params name='klog' endparams /* load klog under linux only */ run if IsLinux() input 'klog' load 'ommysql.so'if $message contains "error" then &nbsp; action &nbsp;&nbsp;&nbsp; type='ommysql.so', queue.mode='disk', queue.highwatermark = 300, &nbsp; &nbsp; action.dbname='events', action.dbuser='uid', &nbsp;
&nbsp; [?action.template='templatename'?] or [?action.sql='insert into
table... values('&amp;$facility&amp;','&amp;$severity&amp;...?] &nbsp; endaction ... or ...define action writeMySQL &nbsp;&nbsp;&nbsp; type='ommysql.so', queue.mode='disk', queue.highwatermark = 300, &nbsp; &nbsp; action.dbname='events', action.dbuser='uid', &nbsp; &nbsp; [?action.template='templatename'?] or [?action.sql='insert into table... values(' &amp; $facility &amp; ',' &nbsp;&amp; $severity &amp;...?] &nbsp; &nbsp;endactionif $message contains "error" then action writeMySQLALTERNATE APPROACHdefine function IsLinux( &nbsp; &nbsp; if $environ contains "linux" then return true else return false )load if IsLinux() 'imklog.so' params name='klog' endparams /* load klog under linux only */ run if IsLinux() input 'klog' load 'ommysql.so'if $message contains "error" then &nbsp; action( &nbsp;&nbsp;&nbsp; type='ommysql.so', queue.mode='disk', queue.highwatermark = 300, &nbsp; &nbsp; action.dbname='events', action.dbuser='uid', &nbsp;
&nbsp; [?action.template='templatename'?] or [?action.sql='insert into
table... values('&amp;$facility&amp;','&amp;$severity&amp;...?] &nbsp;&nbsp;) ... or ...define action writeMySQL( &nbsp;&nbsp;&nbsp; type='ommysql.so', queue.mode='disk', queue.highwatermark = 300, &nbsp; &nbsp; action.dbname='events', action.dbuser='uid', &nbsp;
&nbsp; [?action.template='templatename'?] or [?action.sql='insert into
table... values('&amp;$facility&amp;','&amp;$severity&amp;...?] &nbsp; &nbsp;)if $message contains "error" then action writeMySQL(action.dbname='differentDB')[<a href="rsyslog_conf.html">rsyslog.conf overview</a>]
<h2>Implementation</h2>
RainerScript will be implemented via a hand-crafted LL(1) parser. I was tempted to use yacc, but it turned out the resulting code was not thread-safe and as such did not fit within the context of rsyslog. Also, limited error handling is not a real problem for us: if there is a problem in parsing the configuration file, we stop processing. Guessing what was meant and trying to recover would IMHO not be good choices for something like a syslogd. 
[<a href="manual.html">manual index</a>] [<a href="http://www.rsyslog.com/">rsyslog site</a>]
This documentation is part of the
<a href="http://www.rsyslog.com/">rsyslog</a>
project. 
Copyright &copy; 2008 by <a href="http://www.gerhards.net/rainer">Rainer
Gerhards</a> and
<a href="http://www.adiscon.com/">Adiscon</a>.
Released under the GNU GPL version 3 or higher.
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