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] [--align-start|-a]
11       [--daemon|-d address]
12

DESCRIPTION

14       The fetch function is normally used internally by the graph function to
15       get data from RRDs. fetch will analyze the RRD and try to retrieve the
16       data in the resolution requested.  The data fetched is printed to
17       stdout. *UNKNOWN* data is often represented by the string "NaN"
18       depending on your OS's printf function.
19
20       filename
21               the name of the RRD you want to fetch the data from.
22
23       CF      the consolidation function that is applied to the data you want
24               to fetch (AVERAGE,MIN,MAX,LAST)
25
26       --resolution|-r resolution (default is the highest resolution)
27               the interval you want the values to have (seconds per value).
28               An optional suffix may be used (e.g. "5m" instead of 300
29               seconds).  rrdfetch will try to match your request, but it will
30               return data even if no absolute match is possible. See
31               "RESOLUTION INTERVAL".
32
33       --start|-s start (default end-1day)
34               start of the time series. A time in seconds since epoch
35               (1970-01-01) is required. Negative numbers are relative to the
36               current time. By default, one day worth of data will be
37               fetched. See also "AT-STYLE TIME SPECIFICATION" for a detailed
38               explanation on  ways to specify the start time.
39
40       --end|-e end (default now)
41               the end of the time series in seconds since epoch. See also
42               "AT-STYLE TIME SPECIFICATION" for a detailed explanation of how
43               to specify the end time.
44
45       --align-start|-a
46               Automatically adjust the start time down to be aligned with the
47               resolution.  The end-time is adjusted by the same amount.  This
48               avoids the need for external calculations described in
49               RESOLUTION INTERVAL, though if a specific RRA is desired this
50               will not ensure the start and end fall within its bounds.
51
52       --daemon|-d address
53               Address of the rrdcached daemon. If specified, a "flush"
54               command is sent to the server before reading the RRD files.
55               This allows rrdtool to return fresh data even if the daemon is
56               configured to cache values for a long time.  For a list of
57               accepted formats, see the -l option in the rrdcached manual.
58
59                rrdtool fetch --daemon unix:/var/run/rrdcached.sock /var/lib/rrd/foo.rrd AVERAGE
60
61               Please note that due to thread-safety reasons, the time
62               specified with -s and -e cannot use the complex forms described
63               in "AT-STYLE TIME SPECIFICATION". The only accepted arguments
64               are "simple integers". Positive values are interpreted as
65               seconds since epoch, negative values (and zero) are interpreted
66               as relative to now. So "1272535035" refers to "09:57:15 (UTC),
67               April 29th 2010" and "-3600" means "one hour ago".
68
69   RESOLUTION INTERVAL
70       In order to get RRDtool to fetch anything other than the finest
71       resolution RRA both the start and end time must be specified on
72       boundaries that are multiples of the desired resolution. Consider the
73       following example:
74
75        rrdtool create subdata.rrd -s 10 \
76         DS:ds0:GAUGE:5m:0:U \
77         RRA:AVERAGE:0.5:5m:300h \
78         RRA:AVERAGE:0.5:15m:300h \
79         RRA:AVERAGE:0.5:1h:50d \
80         RRA:MAX:0.5:1h:50d \
81         RRA:AVERAGE:0.5:1d:600d \
82         RRA:MAX:0.5:1d:600d
83
84       This RRD collects data every 10 seconds and stores its averages over 5
85       minutes, 15 minutes, 1 hour, and 1 day, as well as the maxima for 1
86       hour and 1 day.
87
88       Consider now that you want to fetch the 15 minute average data for the
89       last hour.  You might try
90
91        rrdtool fetch subdata.rrd AVERAGE -r 15m -s -1h
92
93       However, this will almost always result in a time series that is NOT in
94       the 15 minute RRA. Therefore, the highest resolution RRA, i.e. 5 minute
95       averages, will be chosen which in this case is not what you want.
96
97       Hence, make sure that
98
99       1. both start and end time are a multiple of 900 ("15m")
100
101       2. both start and end time are within the desired RRA
102
103       So, if time now is called "t", do
104
105        end time == int(t/900)*900,
106        start time == end time - 1hour,
107        resolution == 900.
108
109       Using the bash shell, this could look be:
110
111        TIME=$(date +%s)
112        RRDRES=900
113        rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \
114           -e $(($TIME/$RRDRES*$RRDRES)) -s e-1h
115
116       Or in Perl:
117
118        perl -e '$ctime = time; $rrdres = 900; \
119                 system "rrdtool fetch subdata.rrd AVERAGE \
120                         -r $rrdres -e @{[int($ctime/$rrdres)*$rrdres]} -s e-1h"'
121
122       Or using the --align-start flag:
123
124        rrdtool fetch subdata.rrd AVERAGE -a -r 15m -s -1h
125
126   AT-STYLE TIME SPECIFICATION
127       Apart from the traditional Seconds since epoch, RRDtool does also
128       understand at-style time specification. The specification is called
129       "at-style" after the Unix command at(1) that has moderately complex
130       ways to specify time to run your job at a certain date and time. The
131       at-style specification consists of two parts: the TIME REFERENCE
132       specification and the TIME OFFSET specification.
133
134   TIME REFERENCE SPECIFICATION
135       The time reference specification is used, well, to establish a
136       reference moment in time (to which the time offset is then applied to).
137       When present, it should come first, when omitted, it defaults to now.
138       On its own part, time reference consists of a time-of-day reference
139       (which should come first, if present) and a day reference.
140
141       The time-of-day can be specified as HH:MM, HH.MM, or just HH. You can
142       suffix it with am or pm or use 24-hours clock. Some special times of
143       day are understood as well, including midnight (00:00), noon (12:00)
144       and British teatime (16:00).
145
146       The day can be specified as month-name day-of-the-month and optional a
147       2- or 4-digit year number (e.g. March 8 1999). Alternatively, you can
148       use day-of-week-name (e.g. Monday), or one of the words: yesterday,
149       today, tomorrow. You can also specify the day as a full date in several
150       numerical formats, including MM/DD/[YY]YY, DD.MM.[YY]YY, or YYYYMMDD.
151
152       NOTE1: this is different from the original at(1) behavior, where a
153       single-number date is interpreted as MMDD[YY]YY.
154
155       NOTE2: if you specify the day in this way, the time-of-day is REQUIRED
156       as well.
157
158       Finally, you can use the words now, start, end or epoch as your time
159       reference. Now refers to the current moment (and is also the default
160       time reference). Start (end) can be used to specify a time relative to
161       the start (end) time for those tools that use these categories
162       (rrdfetch, rrdgraph) and epoch indicates the *IX epoch (*IX timestamp 0
163       = 1970-01-01 00:00:00 UTC). epoch is useful to disambiguate between a
164       timestamp value and some forms of abbreviated date/time specifications,
165       because it allows one to use time offset specifications using units,
166       eg. epoch+19711205s unambiguously denotes timestamp 19711205 and not
167       1971-12-05 00:00:00 UTC.
168
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 now, start, end can be abbreviated as n, s, e.
172
173   TIME OFFSET SPECIFICATION
174       The time offset specification is used to add/subtract certain time
175       intervals to/from the time reference moment. It consists of a sign
176       (+ or -) and an amount. The following time units can be used to specify
177       the amount: years, months, weeks, days, hours, minutes, or seconds.
178       These units can be used in singular or plural form, and abbreviated
179       naturally or to a single letter (e.g. +3days, -1wk, -3y). Several time
180       units can be combined (e.g., -5mon1w2d) or concatenated (e.g., -5h45min
181       = -5h-45min = -6h+15min = -7h+1h30m-15min, etc.)
182
183       NOTE3: If you specify time offset in days, weeks, months, or years, you
184       will end with the time offset that may vary depending on your time
185       reference, because all those time units have no single well defined
186       time interval value (1 year contains either 365 or 366 days, 1 month is
187       28 to 31 days long, and even 1 day may be not equal to 24 hours twice a
188       year, when DST-related clock adjustments take place).  To cope with
189       this, when you use days, weeks, months, or years as your time offset
190       units your time reference date is adjusted accordingly without too much
191       further effort to ensure anything about it (in the hope that mktime(3)
192       will take care of this later).  This may lead to some surprising (or
193       even invalid!) results, e.g. 'May 31 -1month' = 'Apr 31' (meaningless)
194       = 'May 1' (after mktime(3) normalization); in the EET timezone '3:30am
195       Mar 29 1999 -1 day' yields '3:30am Mar 28 1999' (Sunday) which is an
196       invalid time/date combination (because of 3am -> 4am DST forward clock
197       adjustment, see the below example).
198
199       In contrast, hours, minutes, and seconds are well defined time
200       intervals, and these are guaranteed to always produce time offsets
201       exactly as specified (e.g. for EET timezone, '8:00 Mar 27 1999 +2 days'
202       = '8:00 Mar 29 1999', but since there is 1-hour DST forward clock
203       adjustment that occurs around 3:00 Mar 28 1999, the actual time
204       interval between 8:00 Mar 27 1999 and 8:00 Mar 29 1999 equals 47 hours;
205       on the other hand, '8:00 Mar 27 1999 +48 hours' = '9:00 Mar 29 1999',
206       as expected)
207
208       NOTE4: The single-letter abbreviation for both months and minutes is m.
209       To disambiguate them, the parser tries to read your mind :) by applying
210       the following two heuristics:
211
212       1. If m is used in context of (i.e. right after the) years, months,
213          weeks, or days it is assumed to mean months, while in the context of
214          hours, minutes, and seconds it means minutes.  (e.g., in -1y6m or
215          +3w1m m is interpreted as months, while in -3h20m or +5s2m m the
216          parser decides for minutes).
217
218       2. Out of context (i.e. right after the + or - sign) the meaning of m
219          is guessed from the number it directly follows.  Currently, if the
220          number's absolute value is below 6 it is assumed that m means
221          months, otherwise it is treated as minutes.  (e.g., -6m == -6m
222          minutes, while +5m == +5 months)
223
224       Final NOTES: Time specification is case-insensitive.  Whitespace can be
225       inserted freely or omitted altogether.  There are, however, cases when
226       whitespace is required (e.g., 'midnight Thu'). In this case you should
227       either quote the whole phrase to prevent it from being taken apart by
228       your shell or use '_' (underscore) or ',' (comma) which also count as
229       whitespace (e.g., midnight_Thu or midnight,Thu).
230
231   TIME SPECIFICATION EXAMPLES
232       Oct 12 -- October 12 this year
233
234       -1month or -1m -- current time of day, only a month before (may yield
235       surprises, see NOTE3 above).
236
237       noon yesterday -3hours -- yesterday morning; can also be specified as
238       9am-1day.
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240       23:59 31.12.1999 -- 1 minute to the year 2000.
241
242       12/31/99 11:59pm -- 1 minute to the year 2000 for imperialists.
243
244       12am 01/01/01 -- start of the new millennium
245
246       end-3weeks or e-3w -- 3 weeks before end time (may be used as start
247       time specification).
248
249       start+6hours or s+6h -- 6 hours after start time (may be used as end
250       time specification).
251
252       931200300 -- 18:45 (UTC), July 5th, 1999 (yes, seconds since 1970 are
253       valid as well).
254
255       19970703 12:45 -- 12:45  July 3th, 1997 (my favorite, and it has even
256       got an ISO number (8601)).
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ENVIRONMENT VARIABLES

259       The following environment variables may be used to change the behavior
260       of "rrdtool fetch":
261
262       RRDCACHED_ADDRESS
263           If this environment variable is set it will have the same effect as
264           specifying the "--daemon" option on the command line. If both are
265           present, the command line argument takes precedence.
266

AUTHOR

268       Tobias Oetiker <tobi@oetiker.ch>
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2721.8.0                             2022-03-14                       RRDFETCH(1)
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