3 rrdfetch - Fetch data from an RRD.
7 B<rrdtool> B<fetch> I<filename> I<CF>
8 S<[B<--resolution>|B<-r> I<resolution>]>
9 S<[B<--start>|B<-s> I<start>]>
10 S<[B<--end>|B<-e> I<end>]>
11 S<[B<--daemon> I<address>]>
15 The B<fetch> function is normally used internally by the graph
16 function to get data from B<RRD>s. B<fetch> will analyze the B<RRD>
17 and try to retrieve the data in the resolution requested.
18 The data fetched is printed to stdout. I<*UNKNOWN*> data is often
19 represented by the string "NaN" depending on your OS's printf
26 the name of the B<RRD> you want to fetch the data from.
30 the consolidation function that is applied to the data you
31 want to fetch (AVERAGE,MIN,MAX,LAST)
33 =item B<--resolution>|B<-r> I<resolution> (default is the highest resolution)
35 the interval you want the values to have (seconds per
36 value). B<rrdfetch> will try to match your request, but it will return
37 data even if no absolute match is possible. B<NB.> See note below.
39 =item B<--start>|B<-s> I<start> (default end-1day)
41 start of the time series. A time in seconds since epoch (1970-01-01)
42 is required. Negative numbers are relative to the current time. By default,
43 one day worth of data will be fetched. See also AT-STYLE TIME SPECIFICATION
44 section for a detailed explanation on ways to specify the start time.
46 =item B<--end>|B<-e> I<end> (default now)
48 the end of the time series in seconds since epoch. See also AT-STYLE
49 TIME SPECIFICATION section for a detailed explanation of how to
52 =item B<--daemon> I<address>
54 Address of the L<rrdcached> daemon. If specified, a C<flush> command is sent
55 to the server before reading the RRD files. This allows B<rrdtool> to return
56 fresh data even if the daemon is configured to cache values for a long time. To
57 specify a UNIX domain socket use the prefix C<unix:>, see example below. Other
58 addresses are interpreted as normal network addresses, i.E<nbsp>e. IPv4 or IPv6
59 addresses in most cases.
61 rrdtool fetch --daemon unix:/var/run/rrdcached.sock /var/lib/rrd/foo.rrd AVERAGE
65 =head2 RESOLUTION INTERVAL
67 In order to get RRDtool to fetch anything other than the finest resolution RRA
68 B<both> the start and end time must be specified on boundaries that are
69 multiples of the desired resolution. Consider the following example:
71 rrdtool create subdata.rrd -s 10 DS:ds0:GAUGE:300:0:U \
72 RRA:AVERAGE:0.5:30:3600 \
73 RRA:AVERAGE:0.5:90:1200 \
74 RRA:AVERAGE:0.5:360:1200 \
75 RRA:MAX:0.5:360:1200 \
76 RRA:AVERAGE:0.5:8640:600 \
79 This RRD collects data every 10 seconds and stores its averages over 5
80 minutes, 15 minutes, 1 hour, and 1 day, as well as the maxima for 1 hour
83 Consider now that you want to fetch the 15 minute average data for the
84 last hour. You might try
86 rrdtool fetch subdata.rrd AVERAGE -r 900 -s -1h
88 However, this will almost always result in a time series that is
89 B<NOT> in the 15 minute RRA. Therefore, the highest resolution RRA,
90 i.e. 5 minute averages, will be chosen which in this case is not
99 both start and end time are a multiple of 900
103 both start and end time are within the desired RRA
107 So, if time now is called "t", do
109 end time == int(t/900)*900,
110 start time == end time - 1hour,
113 Using the bash shell, this could look be:
117 rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \
118 -e $(($TIME/$RRDRES*$RRDRES)) -s e-1h
122 perl -e '$ctime = time; $rrdres = 900; \
123 system "rrdtool fetch subdata.rrd AVERAGE \
124 -r $rrdres -e @{[int($ctime/$rrdres)*$rrdres]} -s e-1h"'
127 =head2 AT-STYLE TIME SPECIFICATION
129 Apart from the traditional I<Seconds since epoch>, RRDtool does also
130 understand at-style time specification. The specification is called
131 "at-style" after the Unix command at(1) that has moderately complex
132 ways to specify time to run your job at a certain date and time. The
133 at-style specification consists of two parts: the B<TIME REFERENCE>
134 specification and the B<TIME OFFSET> specification.
136 =head2 TIME REFERENCE SPECIFICATION
138 The time reference specification is used, well, to establish a reference
139 moment in time (to which the time offset is then applied to). When present,
140 it should come first, when omitted, it defaults to B<now>. On its own part,
141 time reference consists of a I<time-of-day> reference (which should come
142 first, if present) and a I<day> reference.
144 The I<time-of-day> can be specified as B<HH:MM>, B<HH.MM>,
145 or just B<HH>. You can suffix it with B<am> or B<pm> or use
146 24-hours clock. Some special times of day are understood as well,
147 including B<midnight> (00:00), B<noon> (12:00) and British
150 The I<day> can be specified as I<month-name> I<day-of-the-month> and
151 optional a 2- or 4-digit I<year> number (e.g. March 8 1999). Alternatively,
152 you can use I<day-of-week-name> (e.g. Monday), or one of the words:
153 B<yesterday>, B<today>, B<tomorrow>. You can also specify the I<day> as a
154 full date in several numerical formats, including B<MM/DD/[YY]YY>,
155 B<DD.MM.[YY]YY>, or B<YYYYMMDD>.
157 I<NOTE1>: this is different from the original at(1) behavior, where a
158 single-number date is interpreted as MMDD[YY]YY.
160 I<NOTE2>: if you specify the I<day> in this way, the I<time-of-day> is
163 Finally, you can use the words B<now>, B<start>, or B<end> as your time
164 reference. B<Now> refers to the current moment (and is also the default
165 time reference). B<Start> (B<end>) can be used to specify a time
166 relative to the start (end) time for those tools that use these
167 categories (B<rrdfetch>, L<rrdgraph>).
169 Month and day of the week names can be used in their naturally
170 abbreviated form (e.g., Dec for December, Sun for Sunday, etc.). The
171 words B<now>, B<start>, B<end> can be abbreviated as B<n>, B<s>, B<e>.
173 =head2 TIME OFFSET SPECIFICATION
175 The time offset specification is used to add/subtract certain time
176 intervals to/from the time reference moment. It consists of a I<sign>
177 (S<B<+> or B<->>) and an I<amount>. The following time units can be
178 used to specify the I<amount>: B<years>, B<months>, B<weeks>, B<days>,
179 B<hours>, B<minutes>, or B<seconds>. These units can be used in
180 singular or plural form, and abbreviated naturally or to a single
181 letter (e.g. +3days, -1wk, -3y). Several time units can be combined
182 (e.g., -5mon1w2d) or concatenated (e.g., -5h45min = -5h-45min =
183 -6h+15min = -7h+1h30m-15min, etc.)
185 I<NOTE3>: If you specify time offset in days, weeks, months, or years,
186 you will end with the time offset that may vary depending on your time
187 reference, because all those time units have no single well defined
188 time interval value (S<1 year> contains either 365 or 366 days, S<1 month>
189 is 28 to 31 days long, and even S<1 day> may be not equal to 24 hours
190 twice a year, when DST-related clock adjustments take place).
191 To cope with this, when you use days, weeks, months, or years
192 as your time offset units your time reference date is adjusted
193 accordingly without too much further effort to ensure anything
194 about it (in the hope that mktime(3) will take care of this later).
195 This may lead to some surprising (or even invalid!) results,
196 e.g. S<'May 31 -1month'> = S<'Apr 31'> (meaningless) = S<'May 1'>
197 (after mktime(3) normalization); in the EET timezone
198 '3:30am Mar 29 1999 -1 day' yields '3:30am Mar 28 1999' (Sunday)
199 which is an invalid time/date combination (because of 3am -> 4am DST
200 forward clock adjustment, see the below example).
202 In contrast, hours, minutes, and seconds are well defined time
203 intervals, and these are guaranteed to always produce time offsets
204 exactly as specified (e.g. for EET timezone, S<'8:00 Mar 27 1999 +2
205 days'> = S<'8:00 Mar 29 1999'>, but since there is 1-hour DST forward
206 clock adjustment that occurs around S<3:00 Mar 28 1999>, the actual
207 time interval between S<8:00 Mar 27 1999> and S<8:00 Mar 29 1999>
208 equals 47 hours; on the other hand, S<'8:00 Mar 27 1999 +48 hours'> =
209 S<'9:00 Mar 29 1999'>, as expected)
211 I<NOTE4>: The single-letter abbreviation for both B<months> and B<minutes>
212 is B<m>. To disambiguate them, the parser tries to read your S<mind :)>
213 by applying the following two heuristics:
219 If B<m> is used in context of (i.e. right after the) years,
220 months, weeks, or days it is assumed to mean B<months>, while
221 in the context of hours, minutes, and seconds it means minutes.
222 (e.g., in -1y6m or +3w1m B<m> is interpreted as B<months>, while in
223 -3h20m or +5s2m B<m> the parser decides for B<minutes>).
227 Out of context (i.e. right after the B<+> or B<-> sign) the
228 meaning of B<m> is guessed from the number it directly follows.
229 Currently, if the number's absolute value is below 25 it is assumed
230 that B<m> means B<months>, otherwise it is treated as B<minutes>.
231 (e.g., -25m == -25 minutes, while +24m == +24 months)
235 I<Final NOTES>: Time specification is case-insensitive.
236 Whitespace can be inserted freely or omitted altogether.
237 There are, however, cases when whitespace is required
238 (e.g., S<'midnight Thu'>). In this case you should either quote the
239 whole phrase to prevent it from being taken apart by your shell or use
240 '_' (underscore) or ',' (comma) which also count as whitespace
241 (e.g., midnight_Thu or midnight,Thu).
244 =head2 TIME SPECIFICATION EXAMPLES
246 I<Oct 12> -- October 12 this year
248 I<-1month> or I<-1m> -- current time of day, only a month before
249 (may yield surprises, see NOTE3 above).
251 I<noon yesterday -3hours> -- yesterday morning; can also be specified
254 I<23:59 31.12.1999> -- 1 minute to the year 2000.
256 I<12/31/99 11:59pm> -- 1 minute to the year 2000 for imperialists.
258 I<12am 01/01/01> -- start of the new millennium
260 I<end-3weeks> or I<e-3w> -- 3 weeks before end time
261 (may be used as start time specification).
263 I<start+6hours> or I<s+6h> -- 6 hours after start time
264 (may be used as end time specification).
266 I<931225537> -- 18:45 July 5th, 1999
267 (yes, seconds since 1970 are valid as well).
269 I<19970703 12:45> -- 12:45 July 3th, 1997
270 (my favorite, and its even got an ISO number (8601)).
272 =head1 ENVIRONMENT VARIABLES
274 The following environment variables may be used to change the behavior of
275 C<rrdtoolE<nbsp>fetch>:
279 =item B<RRDCACHED_ADDRESS>
281 If this environment variable is set it will have the same effect as specifying
282 the C<--daemon> option on the command line. If both are present, the command
283 line argument takes precedence.
289 Tobias Oetiker E<lt>tobi@oetiker.chE<gt>