From abd0b45c447caa628bde2ceb6406c56bd7b56003 Mon Sep 17 00:00:00 2001 From: Rainer Gerhards Date: Thu, 21 Feb 2008 17:15:44 +0000 Subject: modified ABNF to meet practical needs --- doc/expression.html | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'doc') diff --git a/doc/expression.html b/doc/expression.html index 2b601e86..b2ed7a06 100644 --- a/doc/expression.html +++ b/doc/expression.html @@ -1,8 +1,6 @@ -Expressions - - +Expressions

Expressions

Rsyslog supports expressions at a growing number of places. So @@ -11,7 +9,7 @@ far, they are supported for filtering messages.

C-like comments (/* some c

Formal Definition

Below is the formal definition of expression format (in ABNF, RFC 2234):
-

if_stmt  := "if" expr "then"  # an aid, not part of expression itself

expr     := e_and *("or" e_and)
e_and    := e_cmp *("and" e_cmp)
e_cmp    := val 0*1(cmp_op val)
val      := term *(("+" / "-") 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   := "==" / "!=" / "<>" / "<" / ">" / "<=" / ">=" / "contains" / "startswith"
digit    := %x30-39
alpha    := "a" ... "z" # all letters
alnum    :* alpha / digit / "_"
+

if_stmt  := "if" expr "then"  # an aid, not part of expression itself

expr     := e_and *("or" e_and)
e_and    := e_cmp *("and" e_cmp)
e_cmp    := val 0*1(cmp_op val)
val      := ["-"] term *(("+" / "-") 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   := "==" / "!=" / "<>" / "<" / ">" / "<=" / ">=" / "contains" / "startswith"
digit    := %x30-39
alpha    := "a" ... "z" # all letters
alnum    :* alpha / digit / "_"

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