


RRDFETCH(1)                  rrdtool                  RRDFETCH(1)


NAME
       rrdtool fetch - fetch data from an rrd.

SYNOPSIS
       rrdtool fetch filename CF [--resolution|-r resolution]
       [--start|-s start] [--end|-e end]

DESCRIPTION
       The fetch function is normally used internally by the
       graph function, to get data from RRDs. fetch will analyze
       the RRD and will 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 OSs printf function.

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

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

       --resolution|-r resolution (default is the highest
               resolution)
               what interval should the values have (seconds per
               value). rrdfetch will try to match your request,
               but it will return data even if no absolute match
               is possible.

       --start|-s start (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.

       --end|-e end (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.

       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 Unix command
       at(1) that has moderately complex ways to specify time to
       run your job at.  The at-style specification consists of
       two parts: TIME REFERENCE specification and TIME OFFSET
       specification.



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RRDFETCH(1)                  rrdtool                  RRDFETCH(1)


       TIME REFERENCE SPECIFICATION

       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 now. On its own part, time
       reference consists of time-of-day reference (which should
       come first, if present) and day reference.

       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. The
       few special times of day are understood as well, these
       include 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 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 day as a full date in several
       numerical formats; these include: MM/DD/[YY]YY,
       DD.MM.[YY]YY, YYYYMMDD (NOTE1: this is different from the
       original at(1) behavior, which interprets a single-number
       date as MMDD[YY]YY) NOTE2: if you specify day this way,
       the time-of-day is REQUIRED to be present.

       Finally, you can use words now, start, or end as your time
       reference. Now refers to the current moment (and is also a
       default time reference). Start (end) can be used to
       specify time relative to the start (end) time for those
       tools that use these categories (rrdfetch, rrdgraph).

       Month and weekday 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 to n,
       s, e.

       TIME OFFSET SPECIFICATION

       Time offset specification is used to add (or subtract)
       certain time interval to (from) the time reference moment.
       It consists of sign (+ or -) and amount. The following
       time units can be used to specify the amount: years,
       months, weeks, days, hours, minutes, seconds, 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.)

       NOTE3: 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 reference, because all those time
       units have no single well defined time interval value



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RRDFETCH(1)                  rrdtool                  RRDFETCH(1)


       (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 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 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 adjustment 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)

       NOTE4: The single-letter abbreviation for both months and
       minutes is m. To disambiguate, 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
          means months, while in -3h20m or +5s2m m means 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 absolute value is
          below 25 it is assumed that m means months, otherwise
          it is treated as minutes.  (e.g., -25m == -25 minutes,
          while +24m == +24 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)







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RRDFETCH(1)                  rrdtool                  RRDFETCH(1)


       TIME SPECIFICATION EXAMPLES

       Oct 12 -- October 12 this year

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

       noon yesterday -3hours -- yesterday morning; can be put
       also 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)

       931225537 -- 18:45  July 5th, 1999 (yes, seconds since
       1970 are valid as well)

       19970703 12:45 -- 12:45  July 3th, 1997 (not quote
       standard, but I love this ...)

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


























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