RRDFETCH(1)                         rrdtool                        RRDFETCH(1)



NAME
       rrdfetch - Fetch data from an RRD.

SYNOPSIS
       rrdtool fetch filename CF [--resolution|-r resolution]
       [--start|-s start] [--end|-e end] [--align-start|-a]
       [--daemon|-d address]

DESCRIPTION
       The fetch function is normally used internally by the graph function to
       get data from RRDs. fetch will analyze the RRD and try to retrieve the
       data in the resolution requested.  The data fetched is printed to
       stdout. *UNKNOWN* data is often represented by the string "NaN"
       depending on your OS's printf function.

       filename
               the name of the RRD you want to fetch the data from.

       CF      the consolidation function that is applied to the data you want
               to fetch (AVERAGE,MIN,MAX,LAST)

       --resolution|-r resolution (default is the highest resolution)
               the interval you want the values to have (seconds per value).
               An optional suffix may be used (e.g. "5m" instead of 300
               seconds).  rrdfetch will try to match your request, but it will
               return data even if no absolute match is possible. See
               "RESOLUTION INTERVAL".

       --start|-s start (default end-1day)
               start of the time series. A time in seconds since epoch
               (1970-01-01) is required. Negative numbers are relative to the
               current time. By default, one day worth of data will be
               fetched. See also "AT-STYLE TIME SPECIFICATION" for a detailed
               explanation on  ways to specify the start time.

       --end|-e end (default now)
               the end of the time series in seconds since epoch. See also
               "AT-STYLE TIME SPECIFICATION" for a detailed explanation of how
               to specify the end time.

       --align-start|-a
               Automatically adjust the start time down to be aligned with the
               resolution.  The end-time is adjusted by the same amount.  This
               avoids the need for external calculations described in
               RESOLUTION INTERVAL, though if a specific RRA is desired this
               will not ensure the start and end fall within its bounds.

       --daemon|-d address
               Address of the rrdcached daemon. If specified, a "flush"
               command is sent to the server before reading the RRD files.
               This allows rrdtool to return fresh data even if the daemon is
               configured to cache values for a long time.  For a list of
               accepted formats, see the -l option in the rrdcached manual.

                rrdtool fetch --daemon unix:/var/run/rrdcached.sock /var/lib/rrd/foo.rrd AVERAGE

               Please note that due to thread-safety reasons, the time
               specified with -s and -e cannot use the complex forms described
               in "AT-STYLE TIME SPECIFICATION". The only accepted arguments
               are "simple integers". Positive values are interpreted as
               seconds since epoch, negative values (and zero) are interpreted
               as relative to now. So "1272535035" refers to "09:57:15 (UTC),
               April 29th 2010" and "-3600" means "one hour ago".

   RESOLUTION INTERVAL
       In order to get RRDtool to fetch anything other than the finest
       resolution RRA both the start and end time must be specified on
       boundaries that are multiples of the desired resolution. Consider the
       following example:

        rrdtool create subdata.rrd -s 10 \
         DS:ds0:GAUGE:5m:0:U \
         RRA:AVERAGE:0.5:5m:300h \
         RRA:AVERAGE:0.5:15m:300h \
         RRA:AVERAGE:0.5:1h:50d \
         RRA:MAX:0.5:1h:50d \
         RRA:AVERAGE:0.5:1d:600d \
         RRA:MAX:0.5:1d:600d

       This RRD collects data every 10 seconds and stores its averages over 5
       minutes, 15 minutes, 1 hour, and 1 day, as well as the maxima for 1
       hour and 1 day.

       Consider now that you want to fetch the 15 minute average data for the
       last hour.  You might try

        rrdtool fetch subdata.rrd AVERAGE -r 15m -s -1h

       However, this will almost always result in a time series that is NOT in
       the 15 minute RRA. Therefore, the highest resolution RRA, i.e. 5 minute
       averages, will be chosen which in this case is not what you want.

       Hence, make sure that

       1. both start and end time are a multiple of 900 ("15m")

       2. both start and end time are within the desired RRA

       So, if time now is called "t", do

        end time == int(t/900)*900,
        start time == end time - 1hour,
        resolution == 900.

       Using the bash shell, this could look be:

        TIME=$(date +%s)
        RRDRES=900
        rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \
           -e $(($TIME/$RRDRES*$RRDRES)) -s e-1h

       Or in Perl:

        perl -e '$ctime = time; $rrdres = 900; \
                 system "rrdtool fetch subdata.rrd AVERAGE \
                         -r $rrdres -e @{[int($ctime/$rrdres)*$rrdres]} -s e-1h"'

       Or using the --align-start flag:

        rrdtool fetch subdata.rrd AVERAGE -a -r 15m -s -1h

   AT-STYLE TIME SPECIFICATION
       Apart from the traditional Seconds since epoch, RRDtool does also
       understand at-style time specification. The specification is called
       "at-style" after the Unix command at(1) that has moderately complex
       ways to specify time to run your job at a certain date and time. The
       at-style specification consists of two parts: the TIME REFERENCE
       specification and the TIME OFFSET specification.

   TIME REFERENCE SPECIFICATION
       The time reference specification is used, well, to establish a
       reference moment in time (to which the time offset is then applied to).
       When present, it should come first, when omitted, it defaults to now.
       On its own part, time reference consists of a time-of-day reference
       (which should come first, if present) and a day reference.

       The time-of-day can be specified as HH:MM, HH.MM, or just HH. You can
       suffix it with am or pm or use 24-hours clock. Some special times of
       day are understood as well, including midnight (00:00), noon (12:00)
       and British teatime (16:00).

       The day can be specified as month-name day-of-the-month and optional a
       2- or 4-digit year number (e.g. March 8 1999). Alternatively, you can
       use day-of-week-name (e.g. Monday), or one of the words: yesterday,
       today, tomorrow. You can also specify the day as a full date in several
       numerical formats, including MM/DD/[YY]YY, DD.MM.[YY]YY, or YYYYMMDD.

       NOTE1: this is different from the original at(1) behavior, where a
       single-number date is interpreted as MMDD[YY]YY.

       NOTE2: if you specify the day in this way, the time-of-day is REQUIRED
       as well.

       Finally, you can use the words now, start, end or epoch as your time
       reference. Now refers to the current moment (and is also the default
       time reference). Start (end) can be used to specify a time relative to
       the start (end) time for those tools that use these categories
       (rrdfetch, rrdgraph) and epoch indicates the *IX epoch (*IX timestamp 0
       = 1970-01-01 00:00:00 UTC). epoch is useful to disambiguate between a
       timestamp value and some forms of abbreviated date/time specifications,
       because it allows one to use time offset specifications using units,
       eg. epoch+19711205s unambiguously denotes timestamp 19711205 and not
       1971-12-05 00:00:00 UTC.

       Month and day of the week names can be used in their naturally
       abbreviated form (e.g., Dec for December, Sun for Sunday, etc.). The
       words now, start, end can be abbreviated as n, s, e.

   TIME OFFSET SPECIFICATION
       The time offset specification is used to add/subtract certain time
       intervals to/from the time reference moment. It consists of a sign
       (+ or -) and an amount. The following time units can be used to specify
       the amount: years, months, weeks, days, hours, minutes, or seconds.
       These units can be used in singular or plural form, and abbreviated
       naturally or to a single letter (e.g. +3days, -1wk, -3y). Several time
       units can be combined (e.g., -5mon1w2d) or concatenated (e.g., -5h45min
       = -5h-45min = -6h+15min = -7h+1h30m-15min, etc.)

       NOTE3: If you specify time offset in days, weeks, months, or years, you
       will end with the time offset that may vary depending on your time
       reference, because all those time units have no single well defined
       time interval value (1 year contains either 365 or 366 days, 1 month is
       28 to 31 days long, and even 1 day may be not equal to 24 hours twice a
       year, when DST-related clock adjustments take place).  To cope with
       this, when you use days, weeks, months, or years as your time offset
       units your time reference date is adjusted accordingly without too much
       further effort to ensure anything about it (in the hope that mktime(3)
       will take care of this later).  This may lead to some surprising (or
       even invalid!) results, e.g. 'May 31 -1month' = 'Apr 31' (meaningless)
       = 'May 1' (after mktime(3) normalization); in the EET timezone '3:30am
       Mar 29 1999 -1 day' yields '3:30am Mar 28 1999' (Sunday) which is an
       invalid time/date combination (because of 3am -> 4am DST forward clock
       adjustment, see the below example).

       In contrast, hours, minutes, and seconds are well defined time
       intervals, and these are guaranteed to always produce time offsets
       exactly as specified (e.g. for EET timezone, '8:00 Mar 27 1999 +2 days'
       = '8:00 Mar 29 1999', but since there is 1-hour DST forward clock
       adjustment that occurs around 3:00 Mar 28 1999, the actual time
       interval between 8:00 Mar 27 1999 and 8:00 Mar 29 1999 equals 47 hours;
       on the other hand, '8:00 Mar 27 1999 +48 hours' = '9:00 Mar 29 1999',
       as expected)

       NOTE4: The single-letter abbreviation for both months and minutes is m.
       To disambiguate them, the parser tries to read your mind :) by applying
       the following two heuristics:

       1. If m is used in context of (i.e. right after the) years, months,
          weeks, or days it is assumed to mean months, while in the context of
          hours, minutes, and seconds it means minutes.  (e.g., in -1y6m or
          +3w1m m is interpreted as months, while in -3h20m or +5s2m m the
          parser decides for minutes).

       2. Out of context (i.e. right after the + or - sign) the meaning of m
          is guessed from the number it directly follows.  Currently, if the
          number's absolute value is below 6 it is assumed that m means
          months, otherwise it is treated as minutes.  (e.g., -6m == -6m
          minutes, while +5m == +5 months)

       Final NOTES: Time specification is case-insensitive.  Whitespace can be
       inserted freely or omitted altogether.  There are, however, cases when
       whitespace is required (e.g., 'midnight Thu'). In this case you should
       either quote the whole phrase to prevent it from being taken apart by
       your shell or use '_' (underscore) or ',' (comma) which also count as
       whitespace (e.g., midnight_Thu or midnight,Thu).

   TIME SPECIFICATION EXAMPLES
       Oct 12 -- October 12 this year

       -1month or -1m -- current time of day, only a month before (may yield
       surprises, see NOTE3 above).

       noon yesterday -3hours -- yesterday morning; can also be specified as
       9am-1day.

       23:59 31.12.1999 -- 1 minute to the year 2000.

       12/31/99 11:59pm -- 1 minute to the year 2000 for imperialists.

       12am 01/01/01 -- start of the new millennium

       end-3weeks or e-3w -- 3 weeks before end time (may be used as start
       time specification).

       start+6hours or s+6h -- 6 hours after start time (may be used as end
       time specification).

       931200300 -- 18:45 (UTC), July 5th, 1999 (yes, seconds since 1970 are
       valid as well).

       19970703 12:45 -- 12:45  July 3th, 1997 (my favorite, and it has even
       got an ISO number (8601)).

ENVIRONMENT VARIABLES
       The following environment variables may be used to change the behavior
       of "rrdtool fetch":

       RRDCACHED_ADDRESS
           If this environment variable is set it will have the same effect as
           specifying the "--daemon" option on the command line. If both are
           present, the command line argument takes precedence.

AUTHOR
       Tobias Oetiker <tobi@oetiker.ch>



1.8.0                             2022-03-14                       RRDFETCH(1)
