RRDFETCH(1)                         rrdtool                        RRDFETCH(1)



NNAAMMEE
       rrdfetch - 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 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 RRRRDD 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)

       ----rreessoolluuttiioonn|--rr _r_e_s_o_l_u_t_i_o_n (default is the highest resolution)
               the interval you want the values to have (seconds per value).
               rrrrddffeettcchh 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)
               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.

       ----eenndd|--ee _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.

   RREESSOOLLUUTTIIOONN IINNTTEERRVVAALL
       In order to get RRDtool to fetch anything other than the finest
       resolution RRA bbootthh 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 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 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"'

   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 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 TTIIMMEE RREEFFEERREENNCCEE
       specification and the TTIIMMEE OOFFFFSSEETT specification.

   TTIIMMEE RREEFFEERREENNCCEE SSPPEECCIIFFIICCAATTIIOONN
       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 nnooww.
       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 HHHH::MMMM, HHHH..MMMM, or just HHHH. You can
       suffix it with aamm or ppmm or use 24-hours clock. Some special times of
       day are understood as well, including 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 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: yyeesstteerrddaayy,
       ttooddaayy, ttoommoorrrrooww. You can also specify the _d_a_y as a full date in several
       numerical formats, including MMMM//DDDD//[[YYYY]]YYYY, DDDD..MMMM..[[YYYY]]YYYY, or YYYYYYYYMMMMDDDD.

       _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 nnooww, ssttaarrtt, or eenndd as your time
       reference. NNooww refers to the current moment (and is also the default
       time reference). SSttaarrtt (eenndd) can be used to specify a time relative to
       the start (end) time for those tools that use these categories
       (rrrrddffeettcchh, rrdgraph).

       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 nnooww, ssttaarrtt, eenndd can be abbreviated as nn, ss, ee.

   TTIIMMEE OOFFFFSSEETT SSPPEECCIIFFIICCAATTIIOONN
       The time offset specification is used to add/subtract certain 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: yyeeaarrss, mmoonntthhss, wweeeekkss, ddaayyss, hhoouurrss, mmiinnuutteess, or sseeccoonnddss.
       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.)

       _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 reference date is adjusted accordingly without 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 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 mmoonntthhss and mmiinnuutteess is mm.
       To disambiguate them, 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 is interpreted as mmoonntthhss, while in -3h20m or +5s2m mm the
          parser decides for 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's 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 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 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 (my favorite, and its even got
       an ISO number (8601)).

AAUUTTHHOORR
       Tobias Oetiker <tobi@oetiker.ch>



1.3.9                             2008-03-15                       RRDFETCH(1)
