1 # rpnexpr.pod - Torrus RPN expressions guide
2 # Copyright (C) 2002 Stanislav Sinyagin
4 # This program is free software; you can redistribute it and/or modify
5 # it under the terms of the GNU General Public License as published by
6 # the Free Software Foundation; either version 2 of the License, or
7 # (at your option) any later version.
9 # This program is distributed in the hope that it will be useful,
10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 # GNU General Public License for more details.
14 # You should have received a copy of the GNU General Public License
15 # along with this program; if not, write to the Free Software
16 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
18 # $Id: rpnexpr.pod.in,v 1.1 2010-12-27 00:04:31 ivan Exp $
19 # Stanislav Sinyagin <ssinyagin@yahoo.com>
23 =head1 RPN expressions in Torrus
25 In Torrus framework, RPN expressions are the superset of those
26 in RRDtool version 1.0. See the C<rrdtool graph> manual at
27 E<lt>http://oss.oetiker.ch/rrdtool/doc/rrdgraph_rpn.en.htmlE<gt>.
29 =head2 New functions added
35 Pops two arguments from stack, and pushes 0 if the arguments are equal,
40 These functions pop two arguments from stack, and push back the result of
41 logical operation. Unlike C operators,
45 Pops one value from stack and pushes 0 if the argument is nonzero,
50 Pops one value from stack and pushes the absolute value of it.
54 Pushes the current time, in seconds since Epoch.
58 Equivalent of C<%>, the modulo operator. In Torrus parameter value,
59 percent sign is reserved for parameter substitution.
63 Returns zero if the argument is undefined, and the argument's numeric value
68 Returns the positive or negative infinity.
74 In certain context, the values of the datasources can be evaluated
77 The general format for data access is following:
81 C<FUNC@> specifies a special function to be performed on the
84 For monitor expressions, C<T@> returns the timestamp of the data source.
86 For C<rrd-cdef> leaf types and for C<rrd-multigraph> datasource types,
87 the following functions affect the graph shape: C<AVERAGE@>, C<MIN@>,
88 C<MAX@>, and C<LAST@>. They cause the corresponding Consolidation Function
89 being used when creating a graph.
91 C<PATH> specifies the relative name for the data source.
92 If omitted, the current leaf value is taken. If starts with C</>,
93 the path is considered as absolute.
94 Path starting with letter denotes the child of the parent subtree.
95 Double dot (C<../>) in the beginning of the path is interpreted as
96 current parent's parent subtree.
98 C<(OFFSET)> determines the time reference, as described in C<rrdtool fetch>
99 manual. In addition, the word C<LAST> refers to the latest data timestamp
102 C<(OFFSET)> is currently supported in Monitor expressions only.
106 Copyright (c) 2002-2004 Stanislav Sinyagin E<lt>ssinyagin@yahoo.comE<gt>