


     RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))            1111....2222....11113333 ((((2222000000006666----00005555----00004444))))            RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))



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

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

     DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
          The ffffeeeettttcccchhhh function is normally used internally by the graph
          function to get data from RRRRRRRRDDDDs. ffffeeeettttcccchhhh will analyze the RRRRRRRRDDD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RRRRRRRDDD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rrreeeessssoooolllluuuuttttiiiioooonnnn|-rrrr _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). rrrrrrrrddddffffeeeettttcccchhhh will try to match your request,
                  but it will return data even if no absolute match is
                  possible. NNNNBBBB.... See note below.

          --ssssttttaaaarrrrtttt|-ss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eeennnndddd|-ee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RRREEEESSSSOOOOLLLLUUUUTTTTIIIIOOOONNNN IIIINNNNTTTTEEEERRRRVVVVAAAALLLL

          In order to get RRDtool to fetch anything other than the
          finest resolution RRA bbbbooootttthhhh the start and end time must be
          specified on boundaries that are multiples of the desired
          resolution. Consider the following example:









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     RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))            1111....2222....11113333 ((((2222000000006666----00005555----00004444))))            RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))



           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NNNOOOOTTT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AAATTTT----SSSSTTTTYYYYLLLLEEEE TTTTIIIIMMMMEEEE SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNN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



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     RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))            1111....2222....11113333 ((((2222000000006666----00005555----00004444))))            RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))



          _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TTTIIIIMMMMEEEE RRRREEEEFFFFEEEERRRREEEENNNNCCCCEEEE
          specification and the TTTTIIIIMMMMEEEE OOOOFFFFFFFFSSSSEEEETTTT specification.

          TTTTIIIIMMMMEEEE RRRREEEEFFFFEEEERRRREEEENNNNCCCCEEEE SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN

          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 nnnnoooowww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HHHHHHH::::MMMMMMMM, HHHHHHHH....MMMMMMMM, or just
          HHHHHHHH. You can suffix it with aaaammmm or ppppmmmm or use 24-hours clock.
          Some special times of day are understood as well, including
          mmmmiiiiddddnnnniiiigggghhhhtttt (00:00), nnnnoooooooonnnn (12:00) and British tttteeeeaaaattttiiiimmmmeee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yyyeeeesssstttteeeerrrrddddaaaayyyy, ttttooooddddaaaayyyy, ttttoooommmmoooorrrrrrrroooowwww. You can
          also specify the _d_a_y as a full date in several numerical
          formats, including MMMMMMMM////DDDDDDDD////[[[[YYYYYYYY]]]]YYYYYYYY, DDDDDDDD....MMMMMMMM....[[[[YYYYYYYY]]]]YYYYYYYY, or YYYYYYYYYYYYYYYYMMMMMMMMDDDDDDD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nnnoooowwww, ssssttttaaaarrrrtttt, or eeeennnndddd as your
          time reference. NNNNoooowwww refers to the current moment (and is
          also the default time reference). SSSSttttaaaarrrrtttt (eeeennnndddd) can be used to
          specify a time relative to the start (end) time for those
          tools that use these categories (rrrrrrrrddddffffeeeettttcccchhhh, 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 nnnnoooowwww, ssssttttaaaarrrrtttt, eeeennnndddd can be abbreviated
          as nnnn, ssss, eeee.

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

          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: yyyyeeeeaaaarrrrssss, mmmmoooonnnntttthhhhssss,
          wwwweeeeeeeekkkkssss, ddddaaaayyyyssss, hhhhoooouuuurrrrssss, mmmmiiiinnnnuuuutttteeeessss, or sssseeeeccccoooonnnnddddssss. 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



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     RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))            1111....2222....11113333 ((((2222000000006666----00005555----00004444))))            RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))



          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 mmmmoooonnnntttthhhhssss and
          mmmmiiiinnnnuuuutttteeeessss is mmmm. To disambiguate them, the parser tries to read
          your mind :)  by applying the following two heuristics:

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

          2  Out of context (i.e. right after the ++++ or ---- sign) the
             meaning of mm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mm means mmmmoooonnnntttthhhhssss, otherwise it
             is treated as mmmmiiiinnnnuuuutttteeeesss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.



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     RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))            1111....2222....11113333 ((((2222000000006666----00005555----00004444))))            RRRRRRRRDDDDFFFFEEEETTTTCCCCHHHH((((1111))))



          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).

          TTTTIIIIMMMMEEEE SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN EEEEXXXXAAAAMMMMPPPPLLLLEEEESSS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
          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)).

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

















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