RRDFETCH(1)                         rrdtool                        RRDFETCH(1)



NNAAMMEE
       rrdtool fetch - fetch data from an rrd.

SSYYNNOOPPSSIISS
       rrrrddttooooll ffeettcchh _f_i_l_e_n_a_m_e _C_F [----rreessoolluuttiioonn|--rr _r_e_s_o_l_u_t_i_o_n]
       [----ssttaarrtt|--ss _s_t_a_r_t] [----eenndd|--ee _e_n_d]

DDEESSCCRRIIPPTTIIOONN
       The ffeettcchh function is normally used internally by the graph function,
       to get data from RRRRDDs. ffeettcchh will analyze the RRRRDD and will 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 OSs printf function.

       _f_i_l_e_n_a_m_e
               the name of the RRRRDD you want to fetch the data from.

       _C_F      which consolidation function should have been applied to the
               data you want to fetch? (AVERAGE,MIN,MAX,LAST)

       ----rreessoolluuttiioonn|--rr _r_e_s_o_l_u_t_i_o_n (default is the highest resolution)
               what interval should the values have (seconds per value). rrrrdd--
               ffeettcchh will try to match your request, but it will return data
               even if no absolute match is possible. NNBB.. See note below.

       ----ssttaarrtt|--ss _s_t_a_r_t (default end-1day)
               when should the data begin. 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 start time.

       ----eenndd|--ee _e_n_d (default now)
               when should the data end. Time in seconds since epoch. See also
               AT-STYLE TIME SPECIFICATION section for a detailed explanation
               of how to specify end time.

       RREESSOOLLUUTTIIOONN IINNTTEERRVVAALL

       In order to get rrdtool to fetch anything other than the finest resolu-
       tion RRA bbootthh the start and end time must be specified on boundaries
       that are multiples of the wanted 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 too fetch the 15 minute average data for
       last hour.  So you might try

        rrdtool fetch subdata.rrd AVERAGE -r 900 -s -1h

       However, this will almost always result in a time series that is NNOOTT 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 wanted RRA

       So, if time now is called "t",

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

       In e.g. bash this could look as:

        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"'

       AATT--SSTTYYLLEE TTIIMMEE SSPPEECCIIFFIICCAATTIIOONN

       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 Unix command _a_t(1) that has moderately complex ways to
       specify time to run your job at.  The at-style specification consists
       of two parts: TTIIMMEE RREEFFEERREENNCCEE specification and TTIIMMEE OOFFFFSSEETT specifica-
       tion.

       TTIIMMEE RREEFFEERREENNCCEE SSPPEECCIIFFIICCAATTIIOONN

       Time reference specification is used, well,... to establish a reference
       moment in time (for time offset to be applied to). When present, it
       should come first, when omitted, it defaults to nnooww. On its own part,
       time reference consists of _t_i_m_e_-_o_f_-_d_a_y reference (which should come
       first, if present) and _d_a_y reference.

       _T_i_m_e_-_o_f_-_d_a_y can be specified as HHHH::MMMM, HHHH..MMMM, or just HHHH, you can suf-
       fix it with aamm or ppmm or use 24-hours clock. The few special times of
       day are understood as well, these include mmiiddnniigghhtt (00:00), nnoooonn
       (12:00) and British tteeaattiimmee (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 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: yyeesstteerrddaayy, ttooddaayy,
       ttoommoorrrrooww.  You can also specify _d_a_y as a full date in several numerical
       formats; these include: MMMM//DDDD//[[YYYY]]YYYY, DDDD..MMMM..[[YYYY]]YYYY, YYYYYYYYMMMMDDDD.

       _N_O_T_E_1: this is different from the original _a_t(1) behavior, which inter-
       prets a single-number date as MMDD[YY]YY.

       _N_O_T_E_2: if you specify _d_a_y this way, the _t_i_m_e_-_o_f_-_d_a_y is REQUIRED to be
       present.

       Finally, you can use words nnooww, ssttaarrtt, or eenndd as your time reference.
       NNooww refers to the current moment (and is also a default time refer-
       ence). SSttaarrtt (eenndd) can be used to specify time relative to the start
       (end) time for those tools that use these categories (rrdfetch, rrd-
       graph).

       Month and weekday names can be used in their naturally abbreviated form
       (e.g., Dec for December, Sun for Sunday, etc.). The words nnooww, ssttaarrtt,
       eenndd can be abbreviated to nn, ss, ee.

       TTIIMMEE OOFFFFSSEETT SSPPEECCIIFFIICCAATTIIOONN

       Time offset specification is used to add (or subtract) certain time
       interval to (from) the time reference moment. It consists of _s_i_g_n
       (++ or --) and _a_m_o_u_n_t. The following time units can be used to specify
       the _a_m_o_u_n_t: yyeeaarrss, mmoonntthhss, wweeeekkss, ddaayyss, hhoouurrss, mmiinnuutteess, sseeccoonnddss, these
       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 together (e.g., -5mon1w2d), as well as several time offsets
       can be 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 you time ref-
       erence, 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 taking
       too much further 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 sur-
       prising (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' (Sun-
       day) which is invalid time/date combination (because of 3am -> 4am DST
       forward clock adjustment, see the below example).  On the other hand,
       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 adjust-
       ment takes place 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 mmoonntthhss and mmiinnuutteess is mm.
       To disambiguate, the parser tries to read your mind :) by applying the
       following two heuristics:

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

       2  Out of context (i.e. right after the ++ or -- sign) the meaning of mm
          is guessed from the number it directly follows.  Currently, if the
          number absolute value is below 25 it is assumed that mm means mmoonntthhss,
          otherwise it is treated as mmiinnuutteess.  (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 midnight,Thu)

       TTIIMMEE SSPPEECCIIFFIICCAATTIIOONN EEXXAAMMPPLLEESS

       _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 the NOTE3 above)

       _n_o_o_n _y_e_s_t_e_r_d_a_y _-_3_h_o_u_r_s -- yesterday morning; can be put also 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 imperialists

       _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 (not quote standard, but I love
       this ...)

AAUUTTHHOORR
       Tobias Oetiker <oetiker@ee.ethz.ch>



1.0.40                            2002-07-31                       RRDFETCH(1)
