1RRDFETCH(1) rrdtool RRDFETCH(1)
2
6 rrdfetch - Fetch data from an RRD.
7
9 rrdtool fetch filename CF [--resolution|-r resolution]
10 [--start|-s start] [--end|-e end] [--daemon address]
11
13 The fetch function is normally used internally by the graph function to
14 get data from RRDs. fetch will analyze the RRD and try to retrieve the
15 data in the resolution requested. The data fetched is printed to
16 stdout. *UNKNOWN* data is often represented by the string "NaN"
17 depending on your OS's printf function.
18 filename
20 the name of the RRD you want to fetch the data from.
21 CF the consolidation function that is applied to the data you want
23 to fetch (AVERAGE,MIN,MAX,LAST)
24 --resolution|-r resolution (default is the highest resolution)
26 the interval you want the values to have (seconds per value).
27 rrdfetch will try to match your request, but it will return
28 data even if no absolute match is possible. NB. See note below.
29 --start|-s start (default end-1day)
31 start of the time series. A time in seconds since epoch
32 (1970-01-01) is required. Negative numbers are relative to the
33 current time. By default, one day worth of data will be
34 fetched. See also AT-STYLE TIME SPECIFICATION section for a
35 detailed explanation on ways to specify the start time.
36 --end|-e end (default now)
38 the end of the time series in seconds since epoch. See also AT-
39 STYLE TIME SPECIFICATION section for a detailed explanation of
40 how to specify the end time.
41 --daemon address
43 Address of the rrdcached daemon. If specified, a "flush"
44 command is sent to the server before reading the RRD files.
45 This allows rrdtool to return fresh data even if the daemon is
46 configured to cache values for a long time. For a list of
47 accepted formats, see the -l option in the rrdcached manual.
48 rrdtool fetch --daemon unix:/var/run/rrdcached.sock /var/lib/rrd/foo.rrd AVERAGE
50 RESOLUTION INTERVAL
52 In order to get RRDtool to fetch anything other than the finest
53 resolution RRA both the start and end time must be specified on
54 boundaries that are multiples of the desired resolution. Consider the
55 following example:
56 rrdtool create subdata.rrd -s 10 DS:ds0:GAUGE:300:0:U \
58 RRA:AVERAGE:0.5:30:3600 \
59 RRA:AVERAGE:0.5:90:1200 \
60 RRA:AVERAGE:0.5:360:1200 \
61 RRA:MAX:0.5:360:1200 \
62 RRA:AVERAGE:0.5:8640:600 \
63 RRA:MAX:0.5:8640:600
64 This RRD collects data every 10 seconds and stores its averages over 5
66 minutes, 15 minutes, 1 hour, and 1 day, as well as the maxima for 1
67 hour and 1 day.
68 Consider now that you want to fetch the 15 minute average data for the
70 last hour. You might try
71 rrdtool fetch subdata.rrd AVERAGE -r 900 -s -1h
73 However, this will almost always result in a time series that is NOT in
75 the 15 minute RRA. Therefore, the highest resolution RRA, i.e. 5 minute
76 averages, will be chosen which in this case is not what you want.
77 Hence, make sure that
79 1. both start and end time are a multiple of 900
81 2. both start and end time are within the desired RRA
83 So, if time now is called "t", do
85 end time == int(t/900)*900,
87 start time == end time - 1hour,
88 resolution == 900.
89 Using the bash shell, this could look be:
91 TIME=$(date +%s)
93 RRDRES=900
94 rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \
95 -e $(($TIME/$RRDRES*$RRDRES)) -s e-1h
96 Or in Perl:
98 perl -e '$ctime = time; $rrdres = 900; \
100 system "rrdtool fetch subdata.rrd AVERAGE \
101 -r $rrdres -e @{[int($ctime/$rrdres)*$rrdres]} -s e-1h"'
102 AT-STYLE TIME SPECIFICATION
104 Apart from the traditional Seconds since epoch, RRDtool does also
105 understand at-style time specification. The specification is called
106 "at-style" after the Unix command at(1) that has moderately complex
107 ways to specify time to run your job at a certain date and time. The
108 at-style specification consists of two parts: the TIME REFERENCE
109 specification and the TIME OFFSET specification.
110 TIME REFERENCE SPECIFICATION
112 The time reference specification is used, well, to establish a
113 reference moment in time (to which the time offset is then applied to).
114 When present, it should come first, when omitted, it defaults to now.
115 On its own part, time reference consists of a time-of-day reference
116 (which should come first, if present) and a day reference.
117 The time-of-day can be specified as HH:MM, HH.MM, or just HH. You can
119 suffix it with am or pm or use 24-hours clock. Some special times of
120 day are understood as well, including midnight (00:00), noon (12:00)
121 and British teatime (16:00).
122 The day can be specified as month-name day-of-the-month and optional a
124 2- or 4-digit year number (e.g. March 8 1999). Alternatively, you can
125 use day-of-week-name (e.g. Monday), or one of the words: yesterday,
126 today, tomorrow. You can also specify the day as a full date in several
127 numerical formats, including MM/DD/[YY]YY, DD.MM.[YY]YY, or YYYYMMDD.
128 NOTE1: this is different from the original at(1) behavior, where a
130 single-number date is interpreted as MMDD[YY]YY.
131 NOTE2: if you specify the day in this way, the time-of-day is REQUIRED
133 as well.
134 Finally, you can use the words now, start, end or epoch as your time
136 reference. Now refers to the current moment (and is also the default
137 time reference). Start (end) can be used to specify a time relative to
138 the start (end) time for those tools that use these categories
139 (rrdfetch, rrdgraph) and epoch indicates the *IX epoch (*IX timestamp 0
140 = 1970-01-01 00:00:00 UTC). epoch is useful to disambiguate between a
141 timestamp value and some forms of abbreviated date/time specifications,
142 because it allows to use time offset specifications using units, eg.
143 epoch+19711205s unambiguously denotes timestamp 19711205 and not
144 1971-12-05 00:00:00 UTC.
145 Month and day of the week names can be used in their naturally
147 abbreviated form (e.g., Dec for December, Sun for Sunday, etc.). The
148 words now, start, end can be abbreviated as n, s, e.
149 TIME OFFSET SPECIFICATION
151 The time offset specification is used to add/subtract certain time
152 intervals to/from the time reference moment. It consists of a sign
153 (+ or -) and an amount. The following time units can be used to specify
154 the amount: years, months, weeks, days, hours, minutes, or seconds.
155 These units can be used in singular or plural form, and abbreviated
156 naturally or to a single letter (e.g. +3days, -1wk, -3y). Several time
157 units can be combined (e.g., -5mon1w2d) or concatenated (e.g., -5h45min
158 = -5h-45min = -6h+15min = -7h+1h30m-15min, etc.)
159 NOTE3: If you specify time offset in days, weeks, months, or years, you
161 will end with the time offset that may vary depending on your time
162 reference, because all those time units have no single well defined
163 time interval value (1 year contains either 365 or 366 days, 1 month is
164 28 to 31 days long, and even 1 day may be not equal to 24 hours twice a
165 year, when DST-related clock adjustments take place). To cope with
166 this, when you use days, weeks, months, or years as your time offset
167 units your time reference date is adjusted accordingly without too much
168 further effort to ensure anything about it (in the hope that mktime(3)
169 will take care of this later). This may lead to some surprising (or
170 even invalid!) results, e.g. 'May 31 -1month' = 'Apr 31' (meaningless)
171 = 'May 1' (after mktime(3) normalization); in the EET timezone '3:30am
172 Mar 29 1999 -1 day' yields '3:30am Mar 28 1999' (Sunday) which is an
173 invalid time/date combination (because of 3am -> 4am DST forward clock
174 adjustment, see the below example).
175 In contrast, hours, minutes, and seconds are well defined time
177 intervals, and these are guaranteed to always produce time offsets
178 exactly as specified (e.g. for EET timezone, '8:00 Mar 27 1999 +2 days'
179 = '8:00 Mar 29 1999', but since there is 1-hour DST forward clock
180 adjustment that occurs around 3:00 Mar 28 1999, the actual time
181 interval between 8:00 Mar 27 1999 and 8:00 Mar 29 1999 equals 47 hours;
182 on the other hand, '8:00 Mar 27 1999 +48 hours' = '9:00 Mar 29 1999',
183 as expected)
184 NOTE4: The single-letter abbreviation for both months and minutes is m.
186 To disambiguate them, the parser tries to read your mind :) by applying
187 the following two heuristics:
188 1. If m is used in context of (i.e. right after the) years, months,
190 weeks, or days it is assumed to mean months, while in the context of
191 hours, minutes, and seconds it means minutes. (e.g., in -1y6m or
192 +3w1m m is interpreted as months, while in -3h20m or +5s2m m the
193 parser decides for minutes).
194 2. Out of context (i.e. right after the + or - sign) the meaning of m
196 is guessed from the number it directly follows. Currently, if the
197 number's absolute value is below 25 it is assumed that m means
198 months, otherwise it is treated as minutes. (e.g., -25m == -25
199 minutes, while +24m == +24 months)
200 Final NOTES: Time specification is case-insensitive. Whitespace can be
202 inserted freely or omitted altogether. There are, however, cases when
203 whitespace is required (e.g., 'midnight Thu'). In this case you should
204 either quote the whole phrase to prevent it from being taken apart by
205 your shell or use '_' (underscore) or ',' (comma) which also count as
206 whitespace (e.g., midnight_Thu or midnight,Thu).
207 TIME SPECIFICATION EXAMPLES
209 Oct 12 -- October 12 this year
210 -1month or -1m -- current time of day, only a month before (may yield
212 surprises, see NOTE3 above).
213 noon yesterday -3hours -- yesterday morning; can also be specified as
215 9am-1day.
216 23:59 31.12.1999 -- 1 minute to the year 2000.
218 12/31/99 11:59pm -- 1 minute to the year 2000 for imperialists.
220 12am 01/01/01 -- start of the new millennium
222 end-3weeks or e-3w -- 3 weeks before end time (may be used as start
224 time specification).
225 start+6hours or s+6h -- 6 hours after start time (may be used as end
227 time specification).
228 931225537 -- 18:45 July 5th, 1999 (yes, seconds since 1970 are valid
230 as well).
231 19970703 12:45 -- 12:45 July 3th, 1997 (my favorite, and its even got
233 an ISO number (8601)).
234
236 The following environment variables may be used to change the behavior
237 of "rrdtool fetch":
238 RRDCACHED_ADDRESS
240 If this environment variable is set it will have the same effect as
241 specifying the "--daemon" option on the command line. If both are
242 present, the command line argument takes precedence.
243
245 Tobias Oetiker <tobi@oetiker.ch>
2461.4.8 2013-05-23 RRDFETCH(1)