RRDFETCH(1)                  rrdtool                  RRDFETCH(1)



NNAAMMEE
       rrdfetch - Fetch data from an RRD.

SSYYNNOOPPSSIISS
       rrrrddttooooll ffeettcchh _f_i_l_e_n_a_m_e _C_F [----rreessoolluuttiioonn|--rr _r_e_s_o_l_u_t_i_o_n]
       [----ssttaarrtt|--ss _s_t_a_r_t] [----eenndd|--ee _e_n_d]

DDEESSCCRRIIPPTTIIOONN
       The ffeettcchh function is normally used internally by the
       graph function to get data from RRRRDDs. ffeettcchh will analyze
       the RRRRDD and try to retrieve the data in the resolution
       requested.  The data fetched is printed to stdout.
       _*_U_N_K_N_O_W_N_* data is often represented by the string "NaN"
       depending on your OS's printf function.

       _f_i_l_e_n_a_m_e
               the name of the RRRRDD you want to fetch the data
               from.

       _C_F      the consolidation function that is applied to the
               data you want to fetch (AVERAGE,MIN,MAX,LAST)

       ----rreessoolluuttiioonn|--rr _r_e_s_o_l_u_t_i_o_n (default is the highest resolu-
       tion)
               the interval you want the values to have (seconds
               per value). rrrrddffeettcchh will try to match your
               request, but it will return data even if no abso-
               lute match is possible. NNBB.. See note below.

       ----ssttaarrtt|--ss _s_t_a_r_t (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 section for a detailed
               explanation on  ways to specify the start time.

       ----eenndd|--ee _e_n_d (default now)
               the end of the time series in seconds since epoch.
               See also AT-STYLE TIME SPECIFICATION section for a
               detailed explanation of how to specify the end
               time.

       RREESSOOLLUUTTIIOONN IINNTTEERRVVAALL

       In order to get RRDtool to fetch anything other than the
       finest resolution RRA bbootthh 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:300:0:U \
         RRA:AVERAGE:0.5:30:3600 \
         RRA:AVERAGE:0.5:90:1200 \
         RRA:AVERAGE:0.5:360:1200 \
         RRA:MAX:0.5:360:1200 \
         RRA:AVERAGE:0.5:8640:600 \
         RRA:MAX:0.5:8640:600

       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 900 -s -1h

       However, this will almost always result in a time series
       that is NNOOTT 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

       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 $(echo $(($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"'

       AATT--SSTTYYLLEE TTIIMMEE SSPPEECCIIFFIICCAATTIIOONN

       Apart from the traditional _S_e_c_o_n_d_s _s_i_n_c_e _e_p_o_c_h, RRDtool
       does also understand at-style time specification. The
       specification is called "at-style" after the Unix command
       _a_t(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 TTIIMMEE RREEFFEERREENNCCEE
       specification and the TTIIMMEE OOFFFFSSEETT specification.

       TTIIMMEE RREEFFEERREENNCCEE SSPPEECCIIFFIICCAATTIIOONN

       The time reference specification is used, well, to estab-
       lish 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 nnooww. On its own part, time
       reference consists of a _t_i_m_e_-_o_f_-_d_a_y reference (which
       should come first, if present) and a _d_a_y reference.

       The _t_i_m_e_-_o_f_-_d_a_y can be specified as HHHH::MMMM, HHHH..MMMM, or just
       HHHH. You can suffix it with aamm or ppmm or use 24-hours clock.
       Some special times of day are understood as well, includ-
       ing mmiiddnniigghhtt (00:00), nnoooonn (12:00) and British tteeaattiimmee
       (16:00).

       The _d_a_y can be specified as _m_o_n_t_h_-_n_a_m_e _d_a_y_-_o_f_-_t_h_e_-_m_o_n_t_h
       and optional a 2- or 4-digit _y_e_a_r number (e.g. March 8
       1999). Alternatively, you can use _d_a_y_-_o_f_-_w_e_e_k_-_n_a_m_e (e.g.
       Monday), or one of the words: yyeesstteerrddaayy, ttooddaayy, ttoommoorrrrooww.
       You can also specify the _d_a_y as a full date in several
       numerical formats, including MMMM//DDDD//[[YYYY]]YYYY, DDDD..MMMM..[[YYYY]]YYYY,
       or YYYYYYYYMMMMDDDD.

       _N_O_T_E_1: this is different from the original _a_t(1) behavior,
       where a single-number date is interpreted as MMDD[YY]YY.

       _N_O_T_E_2: if you specify the _d_a_y in this way, the _t_i_m_e_-_o_f_-_d_a_y
       is REQUIRED as well.

       Finally, you can use the words nnooww, ssttaarrtt, or eenndd as your
       time reference. NNooww refers to the current moment (and is
       also the default time reference). SSttaarrtt (eenndd) can be used
       to specify a time relative to the start (end) time for
       those tools that use these categories (rrrrddffeettcchh, rrd-
       graph).

       Month and day of the week names can be used in their natu-
       rally abbreviated form (e.g., Dec for December, Sun for
       Sunday, etc.). The words nnooww, ssttaarrtt, eenndd can be abbrevi-
       ated as nn, ss, ee.

       TTIIMMEE OOFFFFSSEETT SSPPEECCIIFFIICCAATTIIOONN

       The time offset specification is used to add/subtract cer-
       tain time intervals to/from the time reference moment. It
       consists of a _s_i_g_n (++ or --) and an _a_m_o_u_n_t. The following
       time units can be used to specify the _a_m_o_u_n_t: yyeeaarrss,
       mmoonntthhss, wweeeekkss, ddaayyss, hhoouurrss, mmiinnuutteess, or sseeccoonnddss. These
       units can be used in singular or plural form, and abbrevi-
       ated 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.)

       _N_O_T_E_3: 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 ref-
       erence date is adjusted accordingly without too much fur-
       ther effort to ensure anything about it (in the hope that
       _m_k_t_i_m_e(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
       _m_k_t_i_m_e(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)

       _N_O_T_E_4: The single-letter abbreviation for both mmoonntthhss and
       mmiinnuutteess is mm. To disambiguate them, the parser tries to
       read your mind :) by applying the following two heuris-
       tics:

       1  If mm is used in context of (i.e. right after the)
          years, months, weeks, or days it is assumed to mean
          mmoonntthhss, while in the context of hours, minutes, and
          seconds it means minutes.  (e.g., in -1y6m or +3w1m mm
          is interpreted as mmoonntthhss, while in -3h20m or +5s2m mm
          the parser decides for mmiinnuutteess).

       2  Out of context (i.e. right after the ++ or -- sign) the
          meaning of mm is guessed from the number it directly
          follows.  Currently, if the number's absolute value is
          below 25 it is assumed that mm means mmoonntthhss, otherwise
          it is treated as mmiinnuutteess.  (e.g., -25m == -25 minutes,
          while +24m == +24 months)

       _F_i_n_a_l _N_O_T_E_S: 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 mid-
       night,Thu).

       TTIIMMEE SSPPEECCIIFFIICCAATTIIOONN EEXXAAMMPPLLEESS

       _O_c_t _1_2 -- October 12 this year

       _-_1_m_o_n_t_h or _-_1_m -- current time of day, only a month before
       (may yield surprises, see NOTE3 above).

       _n_o_o_n _y_e_s_t_e_r_d_a_y _-_3_h_o_u_r_s -- yesterday morning; can also be
       specified as _9_a_m_-_1_d_a_y.

       _2_3_:_5_9 _3_1_._1_2_._1_9_9_9 -- 1 minute to the year 2000.

       _1_2_/_3_1_/_9_9 _1_1_:_5_9_p_m -- 1 minute to the year 2000 for imperi-
       alists.

       _1_2_a_m _0_1_/_0_1_/_0_1 -- start of the new millennium

       _e_n_d_-_3_w_e_e_k_s or _e_-_3_w -- 3 weeks before end time (may be used
       as start time specification).

       _s_t_a_r_t_+_6_h_o_u_r_s or _s_+_6_h -- 6 hours after start time (may be
       used as end time specification).

       _9_3_1_2_2_5_5_3_7 -- 18:45  July 5th, 1999 (yes, seconds since
       1970 are valid as well).

       _1_9_9_7_0_7_0_3 _1_2_:_4_5 -- 12:45  July 3th, 1997 (my favorite, and
       its even got an ISO number (8601)).

AAUUTTHHOORR
       Tobias Oetiker <tobi@oetiker.ch>



1.2.15                      2006-07-14                RRDFETCH(1)
