Language Reference

This page describes the syntax and capabilities of Bardolph’s scripting language. For information on how to run a script, please see Command-Line Tools.

Internally, launching a script is a two-step process. First, a parser reads the source file and compiles it into a sequence of encoded instructions. Next, a simple virtual machine (VM) executes those instructions. A job-control facility maintains a queue, allowing execution of a sequence of compiled scripts.

Syntax

A script is a plain-text file in which all whitespace is equivalent. You can format it with tabs or even put the entire script on a single line. Comments begin with the ‘#’ character and continue to the end of the line. All keywords are in lower-case text. By convention, script file names have the “.ls” extension, meaning “lightbulb script”.

Here’s an example, showing a comment:

# comment
hue 360 # red
saturation 100    # 100% saturation
brightness 60.0   # 60% brightness
kelvin 2700

set all

If you were to save this in a file called red.ls, you would then run it with:

lsrun red.ls

This script sets the colors of all known lights to a bright shade of red. Note that the set command is what actually causes the lights to adopt the new settings and change their colors. The all parameter causes the given settings to be applied to all of the lights found on the network.

A script sets the color and brightness of the lights, over a given interval, by specifying 5 numbers: hue, saturation, brightness, kelvin, and duration. During execution, the Bardolph virtual machine sends these settings to the lights.

The value you supply for hue is an angle expressed in in degrees, normally between 0 and 360. The values for saturation and brightness are treated as percentages, while kelvin is considered a temperature in °K. The value for duration is expressed in seconds, and tells the light how long to take to transition from its current state to the one you are now specifying. If you never supply a value for duration, it defaults to zero, and transitions occur instantaneously.

All of these numbers except hue must be positive, and may be floating-point values. Percentages above 100 are considered invalid. Angles for hue greater than or equal to 360 are normalized to a number less than 360 by modulo arithmetic.

One easy way to see what colors correspond to these numbers is to use the color wheel in the LIFX mobile app. In that app, you can see values for hue, saturation, and brightness in real time. If you wanted to reproduce a color, you could put the values displayed by the app into a script.

Note

The term color is somewhat ambiguous. Intuitively, you may consider brightness (intensity) to be separate from a bulb’s color. However, for simplicity here, “color” always refers to both the tone of the light and its intensity. Therefore, in this documentation, “setting the color” of a light means that you are specifying the frequency as well as the brightness of the light that the device produces.

Throughout this documentation, color setting is defined as any of the parameters that control this so-called color. The available color settings are hue, saturation, brightness, and kelvin.

When a setting isn’t specified a second time, the VM uses the existing value. For example, the following reuses numbers for saturation, brightness, and kelvin:

hue 120 saturation 100 brightness 50 kelvin 2700 set all
hue 180 set all

This script will:

Set all lights to HSBK of 120, 100, 50, 2700
Set all lights to HSBK of 180, 100, 50, 2700

Any uninitialized values default to zero, or an empty string. This can lead to unwanted results, so each of the values should be set at least once before setting the color of any lights. Or, consider starting your script with get all (the get command is described below).

Names

As described below, the language supports various features that make use of symbolic names. Examples of this are variables and macros. A valid name starts with either an underscore or alphabetic character. The rest of the name can contain letters, numbers, and underscores. For example:

x
_living_room
Bulb_80

Names are handled with case-sensitive logic.

Individual Lights

Scripts can control individual lights by name. For example, if you have a light named “Table”, you can set its color with:

hue 120 saturation 100 brightness 75 kelvin 2700
set "Table"

A light’s name is configured when you do initial setup with the LIFX software.

When they appear in a script, bulb names must be in quotation marks. They can contain spaces, but may not contain a linefeed. For example:

# Ok
on "Chair Side"

# Error
on "Chair
Side"

If a script contains a name for a light that has not been discovered or is otherwise unavailable, an error is sent to the log, but execution of the script continues.

Multi-Zone Lights

With multiple-zone lights, the set command works the same, but you can limit which zones it affects. It can set all of them to the same color, set the color of a single zone, or set it for a range of them. For example, at home I have a Z LED strip, which I named “Strip”. I can set the entire device to one color with:

hue 150 saturation 100 brightness 50 kelvin 2700 duration 1.5
set "Strip"

To set only one zone, add a zone clause with a single number:

set "Strip" zone 5

To set multiple zones, specify a range with starting and ending zone numbers:

set "Strip" zone 0 8

Note that the zone numbers start with zero. If you try use a zone on a light that doesn’t have that capability, an error will be sent to the log, and the light will not be accessed. Unlike Python ranges, the numbers are inclusive. For example, zone 1 3 would include zones 1, 2, and 3.

Power Command

The commands to turn the lights on or off resemble the set command:

off all
on "Table"

This turns off all the lights, and turns on the one named “Table”.

The on and off commands have no effect on the color of the lights. When on executes, each light will have whatever its color was when it was turned off. If a light is already on or off, an otherwise redundant power operation will have no visible effect, although the VM does send the power command to the bulbs.

When applied to a multi-zone light, the entire device is powered on or off; you can’t set the power for individual zones (although you can set the brightness to zero).

Timing Color Changes

Scripts can contain time delays and durations, both of which are are expressed in seconds. A time delay designates the amount of time to wait before transmitting the next command to the lights. The duration value is passed through to the bulbs, and its interpretation is defined by the LIFX API. Basically, by setting a duration, you determine how long it should take the bulb to transition to its new state. For example:

off all time 5 duration 1.5 on all off "Table"

This will:

Immediately turn off all lights instantaneously.
Wait 5 seconds.
Turn on all the lights, but ramp up the brightness over a period of 1.5 seconds.
Wait 5 seconds again.
Dim down the light named “Table” over a period of 1.5 seconds until it is off.

The underlying API has a precision down to milliseconds. For example, all digits are significant in a time parameter of 1.234.

As mentioned above, the existing values for time and duration are re-used with each command. In this example, time is set only once, but there will be the same delay between every action.

Multiple Lights Using and

If you want to set multiple lights at the same time, you can chain them using and

# Uses "and": both go on at the same time after 2 seconds.
time 2 on "Table" and "Chair Side"

This script will:

Wait 2 seconds.
Turn both lights on simultaneously.

This contrasts with:

# Does not use "and": 2-second delay before the second light is turned on.
time 2 on "Table" on "Chair Side"

This script will:

Wait 2 seconds.
Turn on the light named “Table”.
Wait 2 seconds.
Turn on the light named “Chair Side”.

The and keyword works with set, on, and off. When multiple lights are specified this way, the interpreter attempts to change all of the lights at once, with (theoretically) no delay between each one.

If a script specifies zones, the and comes after the zone numbers. This can be convenient for coordinating a multi-zone light with single-zone bulbs. For example, with a multi-zone light named “Strip” and a bulb named “Table”

hue 120 saturation 75 brightness 75 kelvin 2700 duration 1.5
set "Strip" zone 0 5 and "Table"

Here’s an example of simultaneously setting multiple zones on the same light:

set "Strip" zone 2 and "Strip" zone 13 15

How Time Is Measured

It’s important to note that delay time calculations are based on when the script started. The delay is not calculated based on the completion time of the previous instruction.

For example:

time 2
on all
# Do a lot of slow stuff.
off all

The “off” instruction will be executed 2 seconds from the time that the script was started, and the “off” instruction 4 seconds from that start time.

If part of a script takes a long time to execute, the wait time may elapse before the virtual machine is ready for the next instruction. In this case, that instruction gets executed without any timer delay. If delay times are too short for the program to keep up, it will simply keep executing instructions as fast as it can.

Wait for Time of Day

Instead of waiting for a delay to elapse, you can specify the specific time that an action occurs, using the at modifier with the time command. For example, to turn on all the lights at 8:00 a.m.:

time at 8:00 on all

All times are specified using a 24-hour clock, with midnight at 0:00. In this documentation, the parameter supplied in the script is called a time pattern.

A time pattern can contain wildcards to match more than one possible time. For example, to turn on the lights on the hour and turn them off on the half-hour

time at *:00 on all time at *:30 off all

A time pattern can have placeholders for one or two digits with an asterisk. Here are some examples of valid patterns:

2*:00 - matches 21:00, 22:00, and 23:00.
1:*5 - matches 1:05, 1:15, 1:25, 1:35, 1:45 and 1:55.
*:30 - matches on the half-hour.

These are not valid patterns:

* or *:* - matches anything and is therefore meaningless.
12:8* - not a valid time.
**:08 - only one asterisk is necessary.
12:5 - minutes need to be expressed as two digits.

Note that the language is procedural, not declarative. This means that the script is executed from top to bottom. For example, assume you run this script at 8:00 a.m.:

time at 10:00 on all
time at 9:00 off all

This will turn on all the lights at 10:00 a.m., wait 23 hours, and turn them off again the next day.

You can combine patterns to create more complicated behavior. For example, this will turn on the lights the next time it’s either 15 or 45 minutes past the hour:

time at *:15 or *:45 on all

After a scheduled wait, the delay timer is essentially reset. For example:

time at 12:00 on all
time 60 off all

This would turn on all the lights at noon and then turm them off 60 seconds later, which would be at 12:01 p.m.

Pause for Keypress

Instead of using timed delays, a script can wait for a key to be pressed. For example, to simulate a manual traffic light

saturation 100 brightness 80
hue 120 set all
pause hue 50 set all
pause hue 360 set all

This script will:

Set all the lights to green (hue 120).
Wait for the user to press a key.
Set all the lights to yellow (50).
Wait for a keypress.
Turn the lights red (360).

A script can contain both pauses and timed delays. After a pause, the delay timer is reset. For example:

time at 12:00 on all
pause off all
time 10 on all

This script turns on all the lights at 12:00 noon. It then waits for the user to press a key at the keyboard. When a key has been pressed, it turns off all the lights, waits 10 s, and turns them on again.

Wait With No Action

To wait for the next time interval without doing anything:

wait

This can be useful to keep a script active until the last command has been executed. For example:

time 0 hue 120 saturation 90 brightness 50 kelvin 2700
duration 200 set all
time 200 wait

In this example, the set command will take 200 seconds to fully take effect. The script adds a 200-second wait to keep it from exiting before that slow set completes. If a script is waiting in the queue, this prevents that next script from starting before the 200-second duration has elapsed.

Groups and Locations

The set, on, and off commands can be applied to groups and locations. For example, if you have a location called “Living Room”, you can turn them on and set them all to the same color with:

on location "Living Room"
hue 120 saturation 80 brightness 75 kelvin 2700
set location "Living Room"

Continuing the same example, you can also set the color of all the lights in the “Reading Lights” group with:

set group "Reading Lights"

You can combine lights, groups, and locations with the and keyword:

set location "Living Room" and "Table" and group "Reading Lights"

Macro Definitions

A macro can be defined to hold a commonly-used name or number:

define blue 240 define deep 100 define dim 20
define gradual 4
define ceiling "Ceiling Light in the Living Room"
hue blue saturation deep brightness dim duration gradual
set ceiling

A macro can be used for a light name or a value to be used to set a parameter. It can also be used as a zone number with multi-zone lights:

define my_light "Chair Side"
hue 120 saturation 80 brightness 50 kelvin 2700
set my_light

define zone_1 5 define zone_2 10
set "Strip" zone zone_1 zone_2

Macros may refer to other existing macros:

define blue 240
define b blue

A macro can be defined only once, which makes it suitable for constants:

define blue 240
define blue 260 # Error: already defined.

Variables

A variable is somewhat similar to a macro, in that it can hold a value. However, a variable’s contents can be replaced with a new value at run-time. In addition, the current value for a color setting can be copied into a variable. The syntax is:

assign variable value

A variable can contain a number, a string, or a time pattern. Once it has been initialized, it can be used as a name or a value for a color or time setting. For example:

assign the_light "Chair"
on the_light

assign the_room "Living Room"
off group the_room

assign dinner_time 17:00
time at dinner_time on "Table"

An existing variable can be assigned to another. A variable can also get a copy of a color setting. For example:

assign x 120
assign y x     # y now contains 120
hue 240
assign y hue   # y now contains 240

Assignment of one variable to another has by-value semantics:

assign x 120
assign y x
assign x 240    # y still contains 120
hue y           # Sets hue to 120.

In this example, y has an independent copy of the original value of x, even after x has been given a new value.

Mathematical and Logical Expressions

An expression can be used wherever a number or truth value is needed. The syntax for an expression is to contain it in curly braces. For example, to put 5 + 4 into x:

assign x {5 + 4}

Logical expressions also are contained in curly braces:

if {x > 5} off all

The following operators are available:

+ addition
- subtraction or negative
* multiplication
/ division
^ power of
<, <= less than, less than or equal to
>, >= greater than, greater than or equal to
== equals
!= not equal to

The or and and keywords can be combined with comparison operations. Some examples of expressions:

assign a {45 * -3)
assign b { (4 + 5) / 3 }
assign h { a^2 + b^2 }

if {a > 0 and b != 4 or h < 5} on all

Note that * and / have a higher precedence than + and -. The and operator has a higher precedence than or.

assign a {3 + 4 * 5}    # a = 23
assign b {(3 + 4) * 5}  # b = 35

if {5 > 1 or 10 < 100 and 20 == 30 }   # true
  on all

if {(5 > 1 or 10 < 100) and 20 == 30 } # false
  off all

Numerical values in a logical context are coerced to booleans, where 0 is false, and any other value is true.

Registers can provide values:

assign double_brt {brightness * 2}
brightness double_brt
brightness {double_brt / (2 + 10)}

assign double_brt {double_brt - 10}

Routine Definitions

A subprogram, hereafter called a routine can be defined as a sequence of commands. Here’s a simple exmple of a routine being defined and called:

define shut_off_all off all
shut_off_all

A routine can have one or more parameters if the name is followed by the with keyword:

define set_mz with mz_light mz_zone
  set mz_light zone mz_zone

set_mz "Strip" 7

For code readability, you can contain a routine call in square braces. These two lines of code are equivalent:

set_mz "Strip" 7
[set_mz "Strip" 7]

If a routine contains multiple commands, they need to be contained in begin and end keywords:

define partial_shut_off begin
  off group "Living Room"
end

define off_3_seconds with the_light begin
  duration 3
  off the_light
end

# Another example of putting routine calls in optional brackets.
[partial_shut_off]
[off_3_seconds "Chair"]

A routine can call another and pass along incoming parameters. The called routine must already be defined; there currently is no support for forward declarations. As noted above, the parameters are passed by value:

define delayed_off with light_name delay
begin
  time delay
  off light_name
end

define slow_off with light_name delay
begin
  duration 30
  delayed_off light_name delay
end

slow_off "Chair" 10

A routine may not be re-defined. Routine definitions may not be nested:

define a_routine set "Chair"
define a_routine set "Table"  # Error: already defined.

define outer
begin
  # Error: nested definition not allowed.
  define inner on all
end

Variables defined inside a routine are local and go out of scope when the routine returns. Because parameters are passed by value, assignment to a parameter overwrites the local copy but does not affect any variable outside of the routine:

define do_brightness with x
begin
  assign x 50     # Overwrite local copy.
  assigh y 50     # Local variable
  brightness x    # Set brightness to 50.
end

assign x 200
assign y 100
do_brightness y
hue x             # x unchanged: set hue to 200.
saturation y      # y unchanged: set saturation to 100.

Variables assigned outside of a routine are considered global and are visible in all scopes:

assign y 100

define set_global
begin
  assign y 50
end

set_global
saturation y   # Set saturation to 50.

Conditionals

A conditional consists of the if keyword, followed by an expression and one or more commands. It can also have an else clause:

if {x < 5} off all

get "Top"
if {hue < 100} begin
  hue 100
  set "Top"
end

if {x >= 5} begin
   on all
   hue 120 set all
end else begin
   off all
end

Repeat Loops

An infinitely repeating loop looks like:

repeat
  begin
    on all
    off all
  end

Thoretically, this loop will run forever. However, the job control for the VM is designed to support graceful cutoff of a script’s execution. For ambient interior lighting, this is expected to be a common use case.

Use repeat while for a loop based on a logical condition:

repeat while {brightness < 50}
  begin
      brightness {brightness + 0.1}
      set all
  end

To repeat a loop a given number of times:

repeat 10
  begin
    on all
    off all
  end

Interpolation in Loops

Interpolation of values in a loop allows you to choose the start and end points for a setting and the number of steps to take in between. For example, to give a light a hue of 120, and then gradually transition it to 180 in 5 steps:

repeat 5 with the_hue from 120 to 180
  begin
    hue the_hue
    set all
  end

In this example, the_hue will have values of 120, 135, 150, 165, and 180.

A special use case is to cycle the hue 360° over multiple iterations, perhaps in an infinite loop. The cycle keyword causes a value to loop around with modulo 360 logic, stopping one step short of a complete cycle. By starting at zero again, the iteration continues smoothly.

repeat
  repeat 4 with the_hue cycle
    begin
      hue the_hue
      set all
    end

The inner loop gets executed 4 times, with the_hue having values of 0, 90, 180, and 270, the difference being 90°. The next time the loop executes, it starts again at 0, which is equivalent to 360°. This effectively picks up where the previous loop left off.

You can also specify the starting point:

repeat 4 with the_hue cycle 45
# etc.

In this case, the_hue will have values of 45, 135, 225, and 315.

An arithmetic expression can take the place of any numeric value in a repeat loop. You designate such an expression by enclosing it in curly braces. For example:

assign x 7
repeat {5 + x} with y from {x * 4} to {x * 6}
...

# Equivalent to:
repeat 12 with y from 28 to 42
...

Note that the loop limit is calculated only once. In the following example, the loop is executed 5 times, even though light_count is modified in the body of the loop.

assign light_count 5
repeat light_count begin
    # Doesn't affect the number of iterations.
    assign light_count 0
    ...
end

If you want to control the number of iterations dynamically, you can use a repeat while construct.

By Light

To iterate individually over all the lights:

# Turn on all the lights, one-by-one
repeat all as the_light
    on the_light

In this example, the_light is a variable that is initialized to the name of the next light before the body of the loop is executed.

A range of values can be applied to the lights. For example:

repeat all as bulb with brt from 10 to 30
begin
    brightness brt
    set bulb
end

In this case, the number of lights available determines what increment should be added to the index variable, brt. This allows you to distribute a set of values across some lights without knowing how many there are.

For example, if you have 3 lights, the above loop will be executed 3 times, with brt having values of 10, 20, and 30. If you have 5 lights, you get 5 iterations, with brt having values of 10, 15, 20, 25, and 30.

All groups or locations can be enumerated:

repeat group as the_group with the_hue from 120 to 180 begin
    hue the_hue
    set group the_group
end

To iterate over all the lights in a location or group:

repeat in location "Inside" as the_light
    on the_light

repeat in group "Background" as the_light with sat from 70 to 100
begin
    saturation sat
    set the_light
end

Individual lights can be part of a list:

repeat
    in "Top" and "Middle" and "Table" as the_light
    with sat from 80 to 100
begin
    get the_light
    saturation sat
    set the_light
end

They can also be mixed with the members of groups and locations:

repeat
    in "Table" and location "Living Room"
    as the_light
    with brt from 10 to 80
begin
    brightness brt
    set the_light
end

Here’s an example of a nested loop executed for every known group:

repeat group as grp with brt from 40 to 80 begin
    repeat in group grp as light with c_hue cycle begin
        hue c_hue
        set light
    end
end

This loop assigns a different brightness to each group, ranging between 40% and 80%. Within each group, every light gets the same brightness, but their hues are distributed evenly across a 360° range.

Breaking Out of a Loop

You can use a break command to terminate a loop before its normal end condition is met. The innermost loop is halted, but any outer loop continues to execute:

repeat 10 with the_hue from 10 to 360 begin
    repeat all as bulb begin
        get bulb
        if {brigtness > 50}
            break
        brightness {brightness + 10}
        set bulb
    end

    # Execution continues here after the break interrupts the nested loop.
    hue the_hue
    set all
end

A break command outside of a loop is an error that will halt the compilation of a script.

Retrieving Current Color

The get command retrieves the current settings from a single light:

get "Table"
set all

This script retrieves the values of hue, saturation, brightness, and kelvin from the bulb named “Table Lamp”. It then sets all the other lights to the retrieved color. This has the effect of setting the color of all the lights to match “Table”.

A useful pattern for this command is to get a light’s current values, modify one of them, and then update the light. This allows you to effectively change only one setting:

get light
brightness 100
set light

In this example, the light goes to full intensity withou changing colors.

From a multi-zone light, you can retrieve the color of a single zone or the entire device:

get "Strip" zone 5
get "Strip"

Note that you cannot get values for locations, groups, multiple zones, or multiple lights:

# Errors
get "Table Lamp" and "Chair Side"
get all

# Errors
get location "Living Room"
get group "Reading Lights"

# Error
get "Strip" zone 5 6

Raw, Logical, and RGB Units

For me, the HSB coordinate system isn’t especially intuitive. For example, if I want bright green lights, I’ll have to look up an angle for the hue, or maybe memorize which angle corresponds to which percieved color. The RGB color space can make this much easier, because I know what red, green and blue look like.

Using RGB

By specifing certain values for red, green, and blue, you can probably make a pretty good prediction of how a color will look. Most people know that a mix of red and green yields yellow, green plus blue gives you cyan, and red with blue produces purple.

With RGB units, each component’s intensity is expressed as a percentage, which can be given as a floating-point number. For example, to make all your lights a somewhat dim purple, you could have:

units rgb
red 50 green 0 blue 50
set all

As another example, to have white light that is rather bright:

units rgb
define brt 80
red brt green brt blue brt

Internally, the VM converts these values to their HSB equivalents before sending them to the lights.

Note that the setting for kelvin works the same for RGB units as it does for the default logical units. In practiced, I’ve found that it’s easy to just set kelvin to 2700 at the top of the script and not bother with it after that.

Using Raw Units

In the case of logical or RGB units, numerical values in scripts are given in units that are intended to be convenient to humans. However, during communication with the lights, those numbers are mapped to unsigned, 16-bit integer values as specified by the LIFX API.

If you prefer to send unmodified numbers to the lights as specified by that API, you can use raw values (and switch back to logical units as desired). “Raw” refers to an integer between 0 and 65535 that gets transmitted unmodified to the lights. These two actions are equivalent:

units raw
time 10000 duration 2500
hue 30000 saturation 65535 brightness 32767 kelvin 2700 set all

units logical
time 10 duration 2.5
hue 165 saturation 100 brightness 50 kelvin 2700 set all

Note that with raw units, time and duration are rounded to an integer number of milliseconds. With logical or RGB units, time and duration are treated as a floating-point number of seconds.

There’s no limit to the precision of the floating-point value, but because it will be converted to milliseconds, any digits more than 3 places to the right of the decimal point will be insignificant. For example, durations of 2 and 1.9999 are equivalent, while 3 and 2.999 will differ by one millisecond. However, in practice, none of the timing is precise or accurate enough for you to see any difference in behavior for these examples. In my experience, you can’t expect precision much better than 1/10 of a second.

Switching Unit Modes

In general, you’ll probably just pick a mode at the top of your script and not change it. However, if a script does switch modes, some values get re-calculated to preserve the effect on the lights. For example, hue containing 180 in logical units is converted to 32,767 in raw units.

Which settings get changed depends on what kind of transition takes place. For example, when switching from RGB to logical units, there’s no need to convert time or duration. However, hue, saturation, and brightness are initialized, based on the current values of red, green, and blue.

The following table lists which settings are overwritten, and which ones are unaltered, based on what kind of switch occurs:

Changed When Switching Units Mode
From	To	time, dur.	hue	sat.	brt.	red	green	blue
logical	raw	√	√	√	√	—	—	—
raw	logical	√	√	√	√	—	—	—
rgb	raw	√	√	√	√	—	—	—
raw	rgb	√	—	—	—	√	√	√
rgb	logical	—	√	√	√	—	—	—
logical	rgb	—	—	—	—	√	√	√

None of the changes in unit mode affect the contents of kelvin. That value is always considered to be a temperature measured in °K, and never requires conversion.

Note

While in RGB mode, you can still set the values of hue, saturation, or brightness. However, this will have no practical effect; when you set the color of a light, the VM will ignore them. The transition from RGB to logical or raw mode overwrites the contents of hue, saturation, and brightness. Conversely, you can set red, green, or blue, but they are unused if the VM is not in RGB mode. Similarly, switching to RGB from logical or raw mode overwrites anything previously stored in those three settings.

Following is an example that illustrates some of this behavior:

units logical
kelvin 2500
time 1.5 duration 1.5
hue 120 saturation 100 brightness 100

units rgb
# red, green, and blue are overwritten:
#   kelvin = 2500
#   time = 1.5
#   duration = 1.5
#   red = 0
#   green = 100
#   blue = 0
#   hue = 120
#   saturation = 100
#   brightness = 100


time 2.5 duration 3.5
red 0 green 0 blue 100
hue 0 saturation 0 brightness 0
units raw
# time, duration, hue, saturation, brightness are overwritten:
#   time = 2500
#   duration = 3500
#   red = 0
#   green = 0
#   blue = 100
#   hue = 43690
#   saturation = 65535
#   brightness = 65535
#   kelvin = 2500

Outputting Text

Three commands, print, println, and printf, send output to stdout. They all call Python’s own print function, which under most conditions sends text to stdout, typically the user’s terminal emulator.

Because this is not a general-purpose language, the support for text output is a fairly rudimentary implementation. It pretty much passses data along to the underlying Python print function, aided by the string.format method.

You can print any of the settings, such as hue or brightness, as well as variables and constants.

The print and println commands take a single parameter, which is evaluated and sent to stdout. The print command appends a space to its output, while println and printf each append a line feed.

For example to output some settings:

hue 120 saturation 50 brightness 75 kelvin 2000
println "-----"
print hue
print saturation
print brightness
println kelvin
println "-----"

This would generate the output:

-----
120 50 75 2000
-----

Formatted Output

For any kind of non-trivial output, you’ll probably want to use printf, which is a pass-through to Python’s string.format() function.

The printf command has the syntax:

printf <format> [param, ...]

For example, to output the settings:

hue 120 saturation 50 brightness 75 kelvin 2000
printf "{} {} {} {}" hue saturation brightness kelvin

Note that the field placeholders, in the form of {} correspond to the parameters.

Because the compiler relies on the format string to determine the number of parameters, it must be either a literal or a macro.

define fmt "{}"
printf fmt hue
printf "{}" hue

assign fmt2 "{}"
printf fmt2 hue   # ERROR. Must be a literal or a macro.

It’s possible to use named fields, which can give you cleaner code:

printf "{hue} {saturation} {brightness} {kelvin}"

Named fields can be mixed with anonymous ones:

printf "{hue} {saturation} {brightness} {}" kelvin

The output can contain variables and expressions:

assign x 100
assign y 200
printf "{x} {} {}" y {(x + y) / 2}

The output can also contain light names. Here’s an example that iterates over all of the lights, and outputs the settings for each one:

repeat all as light begin
    get the_light
    printf "Light: {the_light} {hue} {saturation} {brightness} {kelvin}"
end

The formatting capabilities impelemented by the Python language are rather extensive and complicated. For more information on how this formatting works, I recommend that you consult the Python documentation: https://docs.python.org/3/library/string.html#formatspec

In terms of data types, note that hue, saturation, brightness, and kelvin are floating-point numbers in logical and RGB modes. In raw mode, these values are integers. Here’s an example where the light settings are displayed, first in raw units, and then in RGB units:

define header_fmt "{:<9}{:>9}{:>9}{:>9}{:>9}"

units raw
println "----- Raw -----"
printf header_fmt "Name" "Hue" "Sat" "Brt" "Kelvin"
repeat all as light begin
    get light
    printf "{light:<9}{hue:>9d}{saturation:>9d}{brightness:>9d}{kelvin:>9d}"
end

units rgb
println ""
println "----- RGB -----"
printf header_fmt "Name" "Red" "Green" "Blue" "Kelvin"
repeat all as light begin
    get light
    printf "{light:<9}{red:>9.2f}{green:>9.2f}{blue:>9.2f}{kelvin:>9.2f}"
end

Notice that the upper printf uses a format of :>9d, which outputs number as decimal integers, right-justified in a field 9 characters long. The RGB numbers are output with 2 decimal points.

When I ran this script on my own lights one evening, I got this output:

----- Raw -----
Name           Hue      Sat      Brt   Kelvin
Bottom       42597    65535    20001     2400
Middle       38957        0    40259     2700
Top          35316    65535    56432     2700

----- RGB -----
Name           Red    Green     Blue   Kelvin
Bottom        0.00     3.05    30.52  2400.00
Middle       61.43    61.43    61.43  2700.00
Top           0.00    66.02    86.11  2700.00

Examples with printf

This code illustrates equivalent behavior using different parameters:

printf "{hue} {saturation} {brightness}"
printf "{} {} {}" hue saturation brightness
printf "{hue} {} {}" saturation brightness
printf "{2} {1} {0}" brightness saturation hue

All of these lines produce the same output. Note that the bottom line in the code uses positional fields, which are a feature of the underlying Python implementation.

Because of the data types of the settings, use of any integer type specifier requires raw mode:

units raw
printf "{:d}" hue   # Ok because hue is an integer in raw mode
printf "{:f}" hue   # Ok because an integer can be converted to float

units logical
printf "{:d}" hue   # ERROR: hue is a floating-point number

Note that light names are Python strings:

println "Furniture group:"
repeat in group "Furniture" as light
    printf "{light:>10s}"

println "Pole group:"
repeat in group "Pole" as light
    printf "{light:>10}"