xttpd - Harmonic tide clock and tide predictor (web server)
] [ -dc color
] [ -Dc color
] [ -df
] [ -ec color
] [ -el y|n
] [ -em
] [ -fc color
] [ -fg color
] [ -ga aspect
] [ -gs d|l|s
] [ -gt y|n
] [ -gw pixels
[ -hf ``format-string''
] [ -in y|n
] [ -lw pixels
] [ -Mc color
] [ -nc color
] [ -pi days
] [ -tl y|n
] [ -u ft|m
] [ -v
[ -z y|n
XTide is a package that provides tide and current predictions in a wide variety
of formats. Graphs, text listings, and calendars can be generated, or a tide
clock can be provided on your desktop.
XTide can work with X-windows, plain text terminals, or the web. This is
accomplished with three separate programs: the interactive interface (
), the non-interactive or command line interface ( tide
and the web interface ( xttpd
is an XTide web server. It provides web-based access to XTide's
tide predictions by allowing a web browser to speak directly to the XTide
program in HTTP. xttpd
can replace httpd
or it can co-exist with
If you run xttpd
with no command line arguments, it will assume that it
is replacing httpd
and try to bind port 80. If you want it to co-exist
with an existing server, or if you do not have privilege to get port 80, give
it the port number as the first command line argument:
% xttpd 8080
You will then need to link it up as http://www.wherever.org:8080/ instead of
just http://www.wherever.org/, but otherwise, no damage done. Similarly, if
you wish to bind a specific address, you can specify that as the first
% xttpd 127.0.0.2
If you need to specify both address and port number, separate the two with a
slash, like this:
% xttpd 127.0.0.2/8080
Once the port is established, xttpd
will try to set its UID and GID to
values that were specified at compile time. If it is unable to do this, it
will log failure messages to syslog and then exit. Consequently, if it is to
be started by someone other than root, that user's UID and GID must be
configured at compile time. Instructions for doing this are available at
For a complete discussion of the command line options and a detailed explanation
of the XTide package, please see the verbose documentation at
Unless a configuration file /etc/xtide.conf
is supplied, you must set the
environment variable HFILE_PATH
to point to the harmonics files that
should have been installed along with the xtide
If a configuration file is used, the first line should consist of the
colon-separated list of harmonics files (e.g. the HFILE_PATH
without the "export HFILE_PATH=" part). The environment variable
takes precedence over the configuration file.
systems the web server xttpd
may optionally be started
at boot time by editing /etc/init.d/xttpd
(setting the PORT
variable and uncommenting out the line). Set the environment variable
to change the mail feedback
Also, note that on Debian systems the tidal harmonics data file are stored in
instead of /usr/local/share/xtide
- -dc color
- Daytime background color in tide graphs (default
- -Dc color
- Color of datum line in tide graphs (default white).
- -df ``format-string''
- strftime(3) style format string for printing dates
(default %Y-%m-%d). Ignored in calendar mode.
- -ec color
- Foreground in tide graphs during outgoing tide (default
- -el y|n
- Select whether or not to draw datum and middle-level lines
in tide graphs (default n).
- The National Ocean Service (NOS) defines both Mean Sea
Level (MSL) and Mean Tide Level (MTL) in terms of averages taken over
observations. The middle-level line is drawn at the midpoint of the
theoretical tidal range, which usually corresponds to the mathematical
mean level of the predictions. This approximates both MSL and MTL, but,
strictly speaking, is equivalent to neither. Moreover, subordinate station
offsets may shift the actual mean so that it no longer falls at the
midpoint of the tidal range. The datum line is drawn at the zero level of
the predictions, which usually corresponds to the station's benchmark, but
this too can be rendered inaccurate by subordinate station offsets.
- -em pSsMm
- Events to suppress (p = phase of moon, S = sunrise, s =
sunset, M = moonrise, m = moonset), or x to suppress none. E.g, to
suppress all sun and moon events, set eventmask to the value pSsMm.
- -fc color
- Foreground in tide graphs during incoming tide (default
- -fg color
- Color of text and other notations (default black).
- -ga aspect
- Aspect for tide graphs (default 1.0). This controls not the
width or height of the window but rather the relative scaling of the X and
Y axes in the plot of the tide curve.
- -gh pixels
- Height for tide graphs (default 312 pixels).
- -gs d|l|s
- Style of graphs and clocks. Valid values: d (default), l
(line), s (semitransparent).
- -gt y|n
- Select whether or not to label tenths of units in tide
graphs (default n).
- -gw pixels
- Width for tide graphs (default 960 pixels).
- -hf ``format-string''
- strftime(3) style format string for printing hour
labels on time axis (default %l).
- -in y|n
- Select whether or not to use inferred values for some
constituents (default n). For expert use only.
- -lw pixels
- Width of line in graph styles l and s (default 2.5
- -mc color
- Color of mark line in graphs (default red).
- -Mc color
- Color of middle-level line in tide graphs (default
- -nc color
- Nighttime background color in tide graphs (default
- -pi days
- Number of days of predictions to generate when no end time
is specified (default 4).
- -tf ``format-string''
- strftime(3) style format string for printing times
(default %l:%M %p %Z).
- -tl y|n
- Select whether or not to draw depth lines on top of the
tide graph (default n).
- -u ft|m
- Preferred units of length (default no preference).
- Print version string and exit.
- -z y|n
- Select whether or not to coerce all time zones to UTC