1RRDFETCH(1)                         rrdtool                        RRDFETCH(1)
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NAME

6       rrdfetch - Fetch data from an RRD.
7

SYNOPSIS

9       rrdtool fetch filename CF [--resolution|-r resolution]
10       [--start|-s start] [--end|-e end] [--daemon address]
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DESCRIPTION

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
19       filename
20               the name of the RRD you want to fetch the data from.
21
22       CF      the consolidation function that is applied to the data you want
23               to fetch (AVERAGE,MIN,MAX,LAST)
24
25       --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
30       --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
37       --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
42       --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
49                rrdtool fetch --daemon unix:/var/run/rrdcached.sock /var/lib/rrd/foo.rrd AVERAGE
50
51   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
57        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
65       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
69       Consider now that you want to fetch the 15 minute average data for the
70       last hour.  You might try
71
72        rrdtool fetch subdata.rrd AVERAGE -r 900 -s -1h
73
74       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
78       Hence, make sure that
79
80       1. both start and end time are a multiple of 900
81
82       2. both start and end time are within the desired RRA
83
84       So, if time now is called "t", do
85
86        end time == int(t/900)*900,
87        start time == end time - 1hour,
88        resolution == 900.
89
90       Using the bash shell, this could look be:
91
92        TIME=$(date +%s)
93        RRDRES=900
94        rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \
95           -e $(($TIME/$RRDRES*$RRDRES)) -s e-1h
96
97       Or in Perl:
98
99        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
103   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
111   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
118       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
123       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
129       NOTE1: this is different from the original at(1) behavior, where a
130       single-number date is interpreted as MMDD[YY]YY.
131
132       NOTE2: if you specify the day in this way, the time-of-day is REQUIRED
133       as well.
134
135       Finally, you can use the words now, start, or end 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).
140
141       Month and day of the week names can be used in their naturally
142       abbreviated form (e.g., Dec for December, Sun for Sunday, etc.). The
143       words now, start, end can be abbreviated as n, s, e.
144
145   TIME OFFSET SPECIFICATION
146       The time offset specification is used to add/subtract certain time
147       intervals to/from the time reference moment. It consists of a sign
148       (+ or -) and an amount. The following time units can be used to specify
149       the amount: years, months, weeks, days, hours, minutes, or seconds.
150       These units can be used in singular or plural form, and abbreviated
151       naturally or to a single letter (e.g. +3days, -1wk, -3y). Several time
152       units can be combined (e.g., -5mon1w2d) or concatenated (e.g., -5h45min
153       = -5h-45min = -6h+15min = -7h+1h30m-15min, etc.)
154
155       NOTE3: If you specify time offset in days, weeks, months, or years, you
156       will end with the time offset that may vary depending on your time
157       reference, because all those time units have no single well defined
158       time interval value (1 year contains either 365 or 366 days, 1 month is
159       28 to 31 days long, and even 1 day may be not equal to 24 hours twice a
160       year, when DST-related clock adjustments take place).  To cope with
161       this, when you use days, weeks, months, or years as your time offset
162       units your time reference date is adjusted accordingly without too much
163       further effort to ensure anything about it (in the hope that mktime(3)
164       will take care of this later).  This may lead to some surprising (or
165       even invalid!) results, e.g. 'May 31 -1month' = 'Apr 31' (meaningless)
166       = 'May 1' (after mktime(3) normalization); in the EET timezone '3:30am
167       Mar 29 1999 -1 day' yields '3:30am Mar 28 1999' (Sunday) which is an
168       invalid time/date combination (because of 3am -> 4am DST forward clock
169       adjustment, see the below example).
170
171       In contrast, hours, minutes, and seconds are well defined time
172       intervals, and these are guaranteed to always produce time offsets
173       exactly as specified (e.g. for EET timezone, '8:00 Mar 27 1999 +2 days'
174       = '8:00 Mar 29 1999', but since there is 1-hour DST forward clock
175       adjustment that occurs around 3:00 Mar 28 1999, the actual time
176       interval between 8:00 Mar 27 1999 and 8:00 Mar 29 1999 equals 47 hours;
177       on the other hand, '8:00 Mar 27 1999 +48 hours' = '9:00 Mar 29 1999',
178       as expected)
179
180       NOTE4: The single-letter abbreviation for both months and minutes is m.
181       To disambiguate them, the parser tries to read your mind :) by applying
182       the following two heuristics:
183
184       1. If m is used in context of (i.e. right after the) years, months,
185          weeks, or days it is assumed to mean months, while in the context of
186          hours, minutes, and seconds it means minutes.  (e.g., in -1y6m or
187          +3w1m m is interpreted as months, while in -3h20m or +5s2m m the
188          parser decides for minutes).
189
190       2. Out of context (i.e. right after the + or - sign) the meaning of m
191          is guessed from the number it directly follows.  Currently, if the
192          number's absolute value is below 25 it is assumed that m means
193          months, otherwise it is treated as minutes.  (e.g., -25m == -25
194          minutes, while +24m == +24 months)
195
196       Final NOTES: Time specification is case-insensitive.  Whitespace can be
197       inserted freely or omitted altogether.  There are, however, cases when
198       whitespace is required (e.g., 'midnight Thu'). In this case you should
199       either quote the whole phrase to prevent it from being taken apart by
200       your shell or use '_' (underscore) or ',' (comma) which also count as
201       whitespace (e.g., midnight_Thu or midnight,Thu).
202
203   TIME SPECIFICATION EXAMPLES
204       Oct 12 -- October 12 this year
205
206       -1month or -1m -- current time of day, only a month before (may yield
207       surprises, see NOTE3 above).
208
209       noon yesterday -3hours -- yesterday morning; can also be specified as
210       9am-1day.
211
212       23:59 31.12.1999 -- 1 minute to the year 2000.
213
214       12/31/99 11:59pm -- 1 minute to the year 2000 for imperialists.
215
216       12am 01/01/01 -- start of the new millennium
217
218       end-3weeks or e-3w -- 3 weeks before end time (may be used as start
219       time specification).
220
221       start+6hours or s+6h -- 6 hours after start time (may be used as end
222       time specification).
223
224       931225537 -- 18:45  July 5th, 1999 (yes, seconds since 1970 are valid
225       as well).
226
227       19970703 12:45 -- 12:45  July 3th, 1997 (my favorite, and its even got
228       an ISO number (8601)).
229

ENVIRONMENT VARIABLES

231       The following environment variables may be used to change the behavior
232       of "rrdtool fetch":
233
234       RRDCACHED_ADDRESS
235           If this environment variable is set it will have the same effect as
236           specifying the "--daemon" option on the command line. If both are
237           present, the command line argument takes precedence.
238

AUTHOR

240       Tobias Oetiker <tobi@oetiker.ch>
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2441.4.4                             2008-09-25                       RRDFETCH(1)
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