heliocron
A simple command line application that integrates with cron
to execute tasks relative to sunset, sunrise and other such solar events.
Table of Contents
Installation
There are several ways to install heliocron
on your device.
1. Pre-compiled binaries
You can download a pre-compiled binary from the releases page.
Here's a quick compatibility table to help choose the correct binary to download:
Platform | Binary |
---|---|
Raspberry Pi 0/1 | heliocron-v0.8.1-arm-unknown-linux-gnueabihf.tar.gz |
Raspberry Pi 2/3/4 | heliocron-v0.8.1-armv7-unknown-linux-gnueabihf.tar.gz |
Linux with a 64bit CPU | heliocron-v0.8.1-x86_64-unknown-linux-gnu.tar.gz |
2. Install with cargo
# make sure you've got an up to date version of rust and cargo installed
# full instructions can be found at https://www.rust-lang.org/tools/install
|
# then install using cargo
3. Build from source
Usage Examples
Delay execution of a command relative to sunrise or sunset
The following code snippet entered into the terminal will wait until sunset on 25th Feb 2020 at the Royal Greenwich Observatory (17:32:17 +00:00) before listing the files and folders contained within the user's home directory.
&&
Integration with cron
for recurring tasks is easy. The following snippet shows a crontab
entry which will run every morning at 2am. heliocron
will wait until 30 minutes before sunrise, before allowing the execution of the turn-on-lights.sh
script.
&&
Show a report of sunrise and sunset times for a given location and date
Display real time data pertaining to the current position of the Sun
Use the poll
subcommand to see what the Sun is doing right now:
The same set of data can be output in machine-readable JSON format.
} }
Supplying the optional --watch
flag will give a second-by-second live view of the position of the Sun.
--watch
and --json
combined also works:
Configuration
heliocron
supports reading some configuration options from a file located at ~/.config/heliocron.toml. Note that this file is not created by default, it is up to the user to create the file correctly, otherwise heliocron
will simply pass over it. In particular, you can set a default latitude and longitude (must provide both, otherwise it will fall back to the default location of the Royal Greenwich Observatory).
# ~/.config/heliocron.toml
# set the default location to Buckingham Palace
= 51.5014
= -0.1419
Now, using heliocron
without providing specific coordinates will yield the following output:
Observe that the location is set according to the contents of the configuration file.
Arguments passed in via the command line will override those set in the configuration file. Perhaps we want to check what is happening over at Windsor Castle without changing the configuration file:
Edge Cases
The chosen event does not occur on the given day
Sometimes, a particular event will never happen on a certain day at a certain location. For example, the Sun never drops below 18° below the horizon in England during the height of summer; astronomical dawn and dusk never occur.
When using the report
subcommand, this is identified like so:
<-
When using the wait
subcommand, an error is raised and the program terminates immediately:
The chosen event occurred some time in the past
If you try and wait
for an event which happened in the past, an error will be raised and the program will terminate immediately:
;
No such error arises if you just want a report
from that date.
Reference
Usage
Options
-
-d, --date
[default: today]Specify the date in ISO 8601 format (YYYY-MM-DD).
-
-l, --latitude
[default: 51.4769]Specify the north/south coordinate of the location. If
--latitude
is passed as a command line option,--longitude
must also be provided.Latitude must be specified in decimal degrees - a number between -90.0 and 90.0 where positive is to the north and negative is to the south.
Can be specified in a file located at ~/.config/heliocron.toml (see Configuration), although note that options provided over the command line take precedence.
-
-o, --longitude
[default: -0.0005]Specify the east/west coordinate of the location. If
--longitude
is passed as a command line option,--latitude
must also be provided.Longitude must be specified in decimal degrees - a number between -180.0 and 180.0 where positive is to the east and negative is to the west.
Can be specified in a file located at ~/.config/heliocron.toml (see Configuration), although note that options provided over the command line take precedence.
-
-t, --time-zone
[default: here and now]Specify the time zone, in [+/-]HH:MM format, at which to calculate and display times.
Subcommands
-
report
Output the dates and times of sunrise, sunset, etc to stdout on the specified date at the specified location.
-
--json
[optional]If this flag is present, the report will be output in JSON format, enabling easier parsing by other programs. If absent, the report is presented in a human-readable format, as displayed in the usage examples above.
Example:
# note that the output has been annotated and prettified in this example to more clearly show the structure { }
-
-
wait
Put the thread to sleep until the chosen event [+ offset] occurs on the specified date at the specified location.
-
-e, --event
[required]Must be one of:
Event Description sunrise
The moment when the upper edge of the solar disk becomes visible above the horizon sunset
The moment when the upper edge of the solar disk disappears below the horizon civil_dawn
The moment when the geometric centre of the Sun reaches 6° below the horizon as it is rising civil_dusk
The moment when the geometric centre of the Sun reaches 6° below the horizon as it is setting nautical_dawn
The moment when the geometric centre of the Sun reaches 12° below the horizon as it is rising nautical_dusk
The moment when the geometric centre of the Sun reaches 12° below the horizon as it is setting astronomical_dawn
The moment when the geometric centre of the Sun reaches 18° below the horizon as it is rising astronomical_dusk
The moment when the geometric centre of the Sun reaches 18° below the horizon as it is setting custom_am
Allows the user to specify the moment when the geometric centre of the Sun reaches a custom number of degrees below the horizon as it is rising custom_pm
Allows the user to specify the moment when the geometric centre of the Sun reaches a custom number of degrees below the horizon as it is setting solar_noon
The moment when the Sun reaches its highest point in the sky -
-a, --altitude
[required if--event
is one of {custom_am
|custom_pm
}]Specify the number of degrees that the geometric centre of the Sun is below the horizon when using a
custom_*
event. Allowed values are between -90.0 and 90.0.If this option is passed for any other event, it is simply ignored.
Example:
# specify the custom event of Jewish dusk, commonly held to be when the centre of the Sun is 8.5° below the horizon as it is setting in the evening
-
-o, --offset
[default: 00:00:00]Specify an offset, either in [-]HH:MM or [-]HH:MM:SS format, from the chosen event. Negative offsets (those which are prefixed with a '
-
' e.g.-01:00
) will set the delay to be before the event, whilst positive offsets will shift the delay after the event. -
--run-missed-task
[optional]If this flag is present, then the process will exit successfully even if the event was missed. This can happen, for example, if the device running
heliocron
goes to sleep and does not wake up until after the event has occurred. Without this flag, if the event is missed by more than 30 seconds, then the task will not be run. -
--tag
[optional]Allows specifying a custom string to describe or otherwise tag the process. When viewing all running processes, e.g. with
htop
, it will then be possible to filter against this tag as it appears on the command line.This option has no other effect on the running of the program.
-
-
poll
Display real time data pertaining to the Sun at the current local time
Note that if
--date
is specified previously as an option, it is ignored in favour of using the current local date.-
--watch
[optional] If this flag is present, the program will continue to run and update the values every second. -
--json
[optional] If this flag is present, the data will be output in JSON format, enabling easier parsing by other programs. If absent, the report is presented in a human-readable format, as displayed in the usage examples above.Example:
# note that the output has been annotated and prettified in this example to more clearly show the structure { }
-