fix wording regarding min/max setting

[rrdtool.git] / doc / rrdfetch.pod

diff --git a/doc/rrdfetch.pod b/doc/rrdfetch.pod
index 7ebd9d6..29f91bc 100644 (file)
--- a/doc/rrdfetch.pod
+++ b/doc/rrdfetch.pod
@@ -8,6 +8,7 @@ B<rrdtool> B<fetch> I<filename> I<CF>
 S<[B<--resolution>|B<-r> I<resolution>]>
 S<[B<--start>|B<-s> I<start>]>
 S<[B<--end>|B<-e> I<end>]>
 S<[B<--resolution>|B<-r> I<resolution>]>
 S<[B<--start>|B<-s> I<start>]>
 S<[B<--end>|B<-e> I<end>]>

+S<[B<--daemon> I<address>]>

 
 =head1 DESCRIPTION
 
 
 =head1 DESCRIPTION
 


@@ -48,6 +49,22 @@ 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.
 
 TIME SPECIFICATION section for a detailed explanation of how to
 specify the end time.
 

+=item B<--daemon> I<address>
+
+Address of the L<rrdcached> daemon. If specified, a C<flush> command is sent
+to the server before reading the RRD files. This allows B<rrdtool> to return
+fresh data even if the daemon is configured to cache values for a long time.
+For a list of accepted formats, see the B<-l> option in the L<rrdcached> manual.
+
+ rrdtool fetch --daemon unix:/var/run/rrdcached.sock /var/lib/rrd/foo.rrd AVERAGE
+
+Please note that due to thread-safety reasons, the time specified with B<-s>
+and B<-e> cannot use the complex forms described in
+L<"AT-STYLE TIME SPECIFICATION">. The only accepted arguments are "simple
+integers". Positive values are interpreted as seconds since epoch, negative
+values (and zero) are interpreted as relative to I<now>. So "1272535035" refers
+to "09:57:15 (UCT), April 29th 2010" and "-3600" means "one hour ago".
+

 =back
 
 =head2 RESOLUTION INTERVAL
 =back
 
 =head2 RESOLUTION INTERVAL


@@ -103,7 +120,7 @@ Using the bash shell, this could look be:
  TIME=$(date +%s)
  RRDRES=900
  rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \
  TIME=$(date +%s)
  RRDRES=900
  rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \

-    -e $(echo $(($TIME/$RRDRES*$RRDRES))) -s e-1h
+    -e $(($TIME/$RRDRES*$RRDRES)) -s e-1h

 
 Or in Perl:
 
 
 Or in Perl:
 


@@ -148,11 +165,16 @@ single-number date is interpreted as MMDD[YY]YY.
 I<NOTE2>: if you specify the I<day> in this way, the I<time-of-day> is
 REQUIRED as well.
 
 I<NOTE2>: if you specify the I<day> in this way, the I<time-of-day> is
 REQUIRED as well.
 

-Finally, you can use the words B<now>, B<start>, or B<end> as your time
+Finally, you can use the words B<now>, B<start>, B<end> or B<epoch> as your time

 reference. B<Now> refers to the current moment (and is also the default
 time reference). B<Start> (B<end>) can be used to specify a time
 relative to the start (end) time for those tools that use these
 reference. B<Now> refers to the current moment (and is also the default
 time reference). B<Start> (B<end>) can be used to specify a time
 relative to the start (end) time for those tools that use these

-categories (B<rrdfetch>, L<rrdgraph>).
+categories (B<rrdfetch>, L<rrdgraph>) and B<epoch> indicates the 
+*IX epoch (*IX timestamp 0 = 1970-01-01 00:00:00 UTC). B<epoch> is
+useful to disambiguate between a timestamp value and some forms
+of abbreviated date/time specifications, because it allows to use 
+time offset specifications using units, eg. B<epoch>+19711205s unambiguously
+denotes timestamp 19711205 and not 1971-12-05 00:00:00 UTC.

 
 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
 
 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


@@ -257,6 +279,22 @@ I<931225537> -- 18:45  July 5th, 1999
 I<19970703 12:45> -- 12:45  July 3th, 1997
 (my favorite, and its even got an ISO number (8601)).
 
 I<19970703 12:45> -- 12:45  July 3th, 1997
 (my favorite, and its even got an ISO number (8601)).
 

+=head1 ENVIRONMENT VARIABLES
+
+The following environment variables may be used to change the behavior of
+C<rrdtoolE<nbsp>fetch>:
+
+=over 4
+
+=item B<RRDCACHED_ADDRESS>
+
+If this environment variable is set it will have the same effect as specifying
+the C<--daemon> option on the command line. If both are present, the command
+line argument takes precedence.
+
+=back
+

 =head1 AUTHOR
 
 =head1 AUTHOR
 

-Tobias Oetiker <oetiker@ee.ethz.ch>
+Tobias Oetiker E<lt>tobi@oetiker.chE<gt>
+