Provided by: trend_1.3-1_amd64 
NAME
trend — a general-purpose, efficient trend graph
SYNOPSIS
trend [-dDSsvlmFgGhtAERIMNTLzfcpue] [-display] [-geometry] [-iconic] ⟨fifo | -⟩ ⟨hist-spec | hist-sz x-sz⟩
[low high]
DESCRIPTION
trend is a general-purpose, efficient trend graph for "live" data. Data is read in ASCII form from a file
or continuously from a FIFO and displayed in real-time into a multi-pass trend (much like a CRT
oscilloscope). trend can be used as a rapid analysis tool for progressive or time-based data series
together with trivial scripting.
trend requires at least a valid fifo to read from and an history specification (hist-spec) or, for advanced
usage, a combination of history size and horizontal size (hist-sz and x-sz respectively). Optionally, to
disable auto-scaling, the vertical limits can be specified directly through the command line via low and
high. The default input format is ASCII, in absolute counting mode. Many settings can be changed directly
during execution.
INPUT
FIFO
To display real-time data you should use a FIFO. Both standard input and named pipes can be used. Standard
input (used for simple pipelining purposes) can be opened by using - instead of a named file. A named FIFO
can be created using the mkfifo(1) command. FIFOs are automatically re-opened upon EOF. See the EXAMPLES
section.
Alternatively you can store your data in a plain file and simply display its last values non-interactively.
When new data is written, the value is plotted and the cursor position is advanced. That is, the graph
scrolling speed is determined by the speed of the data flow. When the number of received values is above
the specified horizontal size, the graph will wrap or scroll, depending on your settings.
ASCII DATA
The default data format is a space/tab/newline-separated series of parseable ASCII numbers; eg:
1 2 3 4 5.1 0642
0x12 -12.4E5 .987
The parser is very lenient, and will silently ignore whatever looks like garbage.
COUNTING MODES
By default all input values are considered absolute and displayed "as is" in a single graph.
The -c [N]mode flag sets an alternate counting mode and the number of available graphs. Available modes
are:
a absolute (default)
i incremental counter
d differential values
In incremental and differential mode, each value is calculated using the previous value as a reference
except for the first, which is taken as absolute. The number of graphs can be specified by prefixing a
multiplier before the counting mode (eg: 2a draws two graphs in absolute mode). See MULTIPLE GRAPHS for
more details on how this affects the input stream.
FORMAT TYPES
Different input formats are supported, as specified by the -f flag. Note however that only the ASCII parser
(the default) silently ignores errors. NaNs and Infinity have special treatment. Internally, trend always
works with double precision floating points: conversion toward these is performed with the default FPU
conversion rules. The actual underlying binary format depends on the host architecture:
a ASCII parser (default)
f binary float
d binary double
s binary short
i binary int
l binary long
SPECIAL VALUES
ASCII and binary floating point input have special treatment for NaNs and Infinity (entered in any
representable form). Both are considered as "undefined values". Undefined values can be highlighted, but
aren't otherwise rendered. If the -e flag is set, Infinity enters an escape sequence instead (See ESCAPE
SEQUENCES)
MULTIPLE GRAPHS
Multiple graphs can be displayed inside a single trend instance by specifying a prefix number N for the -c
flag. The input is interleaved, but otherwise unchanged: the reference value, if needed, is expected to be
seen N times, one for each graph. Thus, for three graphs (A, B and C), the input order is:
[A0 B0 C0]
A1 B1 C1
A2 B2 C2
.. .. ..
The display is updated only once all graph values are read. The color, label and origin for each graph can
be specified through the usual command-line flags, separating each value with a comma; in the same order as
the input. Default colors and labels are assigned if not completely specified.
All graphs share and are affected by the same settings, except for the origin (zero) which can be changed
independently. Filling, values and the examiners only work on the current graph. The current graph can be
cycled dynamically with the TAB key and differentiated using the K key, which cycles between "normal", "dim
others" and "hide others" views. The graph key, if enabled, also highlights the current graph.
ESCAPE SEQUENCES
If escape sequences are enabled (through the -e flag), entering Infinity (in any representable form) will
start an escape sequence. Currently, this feature is not yet implemented: Infinity is simply discarded.
This is reserved for future use as a way to control the trend interface and parameters remotely.
OPTIONS
FLAGS
-d "dimmed" shading mode
-D visible distribution graph
-S enable anti-aliasing
-s "scrolling" mode
-v visible values
-l visible visual/max sync latency
-m visible marker
-F enable filling
-g visible grid
-G grid-spec specify grid resolution
-z zero[,zero...] specify y zero/s
-h help and version info
-t str specify a window title
-A colour background colour
-E colour text (values) colour
-R colour grid colour
-I colour[,colour...] trend colour/s
-M colour marker colour
-N colour interactive examiner colour
-T colour edit mode colour
-L label[,label...] trend label/s
-c mode input number/counting mode (See COUNTING MODES)
-f format input format (See FORMAT TYPES)
-p rate polling rate (hz)
-u show undefined values
-e enable escape sequences (See ESCAPE SEQUENCES)
-display See X(7).
-geometry See X(7).
-iconic See X(7).
HIST-SPEC
An history specification is another convenient form of defining the pair `hist-sz x-sz` for common cases.
An history specification can be in either one of the following formats:
N Sets x-sz to N, and hist-sz to N+1.
N/M Sets hist-sz to N, and x-sz to N/M.
NxM Sets x-sz to N, and hist-sz to N*M.
While this may seem hard at first, trend fifo '60x3' is an easier way of expressing "60 seconds for 3
minutes" and similar idioms.
COLOUR
A colour is specified in hex RGB format, as follows: #RRGGBB, RRGGBB or 0xRRGGBB; some examples:
#FF0000 red
#00FF00 green
#A020F0 purple
GRID-SPEC
A grid specification is of the form:
[[A][+C]][x[B][+C]]
(eg: 1.3, 10+5, 1x10+5, +5x+5; +1x+1 gets the old behaviour) where:
A y grid resolution
B x grid resolution
C draw a mayor line every C normal grid lines
DISPLAY
INTERACTIVE KEYS
ESC quit/exit
TAB cycle current graph
a toggle auto-scaling
A re-scale the graph without activating auto-scaling
d toggle dimmed shading mode
D toggle distribution graph
S toggle anti-aliasing
s switch scrolling mode (wrap-around or scrolling)
v toggle values
l show visual and maximal sync latency
L set limits interactively
m activate a marker on the current cursor position
f toggle filling
g toggle grid
G change grid-spec interactively
z change zero interactively
Z set limits by center and amplitude
p change polling rate interactively
u toggle display of undefined values
k toggle the graph key
K cycle view mode (normal, dim others or hide others)
space pause visualisation (but still continue to consume input to preserve time coherency)
AUTOSCALING
When autoscaling is enabled the graph will be scaled vertically to fit visible values. The grid resolution
is used to add some vertical bounds to the graph. Disabling autoscaling interactively will retain current
limits. When the grid is too dense to be displayed it's deactivated automatically.
LATENCY INDICATOR
The latency indicator shows a 5s average of the visual and maximal sync latency (in seconds). The visual
latency is the time-frame between real value updates and the final output you're seeing: it includes
copy/redraw times, which varies depending on enabled layers, plus video sync. The maximal sync latency is
the maximal time ever required for any received value to be synced with the display: since the display is
updated atomically, values received while redrawing are implicitly delayed. See the UPDATE POLICY section
for further details.
SHADING MODES
The default is to shade uniformly old values to complete transparency. The "dimmed" shading mode draws the
foreground values with full opacity and the others with half opacity.
SCROLLING MODES
The default visualisation mode is "wrap-around": newer values will simply wrap around the screen when new
data arrives. The other available one is "scrolling": new data is always placed at the right edge of the
screen, and older values scrolled on the left.
VALUE INDICATORS
Three value indicators are drawn on the screen: upper limit, lower limit and current value (respectively on
the upper right, lower right and lower left of the screen).
INTERACTIVE EXAMINERS
You can query interactively the graph for any value in the history by clicking with the first mouse button.
This will enable a permanent examiner in the selected position and display up to the three nearest values
in the upper-left corner of the screen. Intersections are projected horizontally, while a small circle will
show the position of the nearest sampled value. The mean value refers to the three intersections.
By holding down the CTRL key while clicking/dragging only "foreground" values will be considered.
When clicking inside the distribution graph, the current count for the selected value is displayed instead.
The examiners can be removed by clicking anywhere with the third mouse button.
DISTRIBUTION GRAPH
D or -D enable a distribution graph on the left side of the window. This is especially useful when
analyzing the continuity of a function or signal. Intensity is proportional to the visible maximum.
FILLING
f or -F enable filling. In standard mode, or when hist-sz is smaller than x-sz, the area between the curve
and zero will be filled. Otherwise, in dimmed mode, the area between the "foreground" and "background"
values is filled instead.
UPDATE POLICY
The fifo is read and managed asynchronously from the graphics. Delays at the display end will not interfere
with the data feed.
The fifo is unbuffered and the feeder thread is synchronously locked on it waiting for new data.
The value is put in the history buffer when a separator character is received after the value, or, for
binary input, when the needed amount of bytes is read (in this case each value is read with a single read
call).
The polling rate (as defined by p or -p and defaulting to 1000) defines how often the history buffer should
be checked for updates and kept in sync with the visual. Values greater than 1000 result in continuous
scanning (note that this only affects the maximal sync latency, and not the display rate, which is handled
automatically).
Syncing occurs atomically, reflecting the actual state at the instant of the update. Scheduler latencies
apply.
ENVIRONMENT
DISPLAY See X(7).
EXAMPLES
Running trend with a named FIFO:
mkfifo fifo
command > fifo &
trend fifo ...
Display the number of current active processes over time:
(while true; do ps -A | wc -l; sleep 1; done) | \
trend - 60x24
Display two graphs:
trend -c2a -L"graph 1, graph 2" fifo ...
DIAGNOSTICS
The trend utility exits 0 on success, and >0 if an error occurs.
ERRORS
trend: producer thread exiting The data stream finished for some reason (the specified file was invalid at
the time of the request). For regular or invalid files this warning is normal.
SEE ALSO
mkfifo(1), stdin(4), fd(4), /usr/share/doc/trend/examples/
AUTHORS
trend is distributed under LGPL (see COPYING) WITHOUT ANY WARRANTY. Copyright(c) 2003-2009 by Yuri D'Elia
<wavexx@thregr.org>.
November 2, 2007