Lua Scripting with REAPER 5 - Part. 1: The Console Output

Build your own REAPER custom actions with scripting !

This series of videos is about learning how to code scripts in Lua for REAPER 5.

If you don't know what ReaScript is, please take a look at the ReaScript Basics series of article on my website:
http://extremraym.com/reascript-basics-part1/

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Any feedback is welcome !

Hello everyone,
this is X-Raym

for a tutorial about
Scripting in REAPER 5

I assume that
you already know REAPER

the sound editing software

and my series of articles called
"ReaScript Basics"

which introduce the concept of ReaScript

in other words,
coding Scripts for REAPER

I will advice you to read the
interview I gave for The REAPER Blog

in which I explain all you have to know
before getting in.

The purpose of this video
is to start coding

by practicing.

This will be done in several steps

We will see in this first video,

how to use the Console, and why.

We will create a new Action/Script

by launching the Action Window,
and then by clicking on ReaScript -> New

The User Scripts directory opens

and I enter a new script name.

"my new script"

I then write the file extension, ".lua".

This extension will determine
what language is use to code this script.

There is two languages that can be
interpreted natively in REAPER, EEL and Lua

Python is possible too for scripting,
but it needs external libraries.

We will choose for its
native interpretation,

but also for its ease of writing,

and for its high performance,
and its flexibility.

If I press save, a window appears.

The "ReaScript Development Environment"

in which you can code your script
directly within REAPER

which is very powerful.

This window is new in REAPER 5,

just as the integration of Lua.

We will start by coding a script
that will display a message in the Console.

The Console is a window that can be
used to develop your script.

For this, you will have to use a function
nammed "ShowConsoleMsg()"

Because it is a native REAPER function,

you will have to set the prefix
"reaper."

As parameters, we put a string
between double quotes ""

If I press CTRL+S again, the script
is saved and executed.

As you can see,
the ReaScript Console Output opens

With the message we set.

If I press start again,

You can see that the message is put
after what was already in the console.

For cleaning the console,
you can press Clear.

The idea behind ShowConsoleMsg
is too display the value of a variable.

We will then create a variable.

We will call it string,
and set "Hellow World!" as value.

Here, we replace the string
by the variable name.

As you can see, it displays
the variable value in the Console.

Just like before.

Now, if I want to display a second line,

we will create a second variable,
with the value "How are you today?"

We now just have to dupplicate the function
ShowConsoleMsg

and to set the second
variable as parameter.

If I display the result...

If I display the result, you can see that the
values are displayed one after the other.

As you can see, the console
hasn't been cleared.

It bothers me as I will have to run the
script several time during its development.

To initialize the console,
we just have to write...

reaper. ShowConsoleMsg()

with an empty string "" as parameter.

It allows to clean the console.

Here is a demo. If I delete all this
and I save + run,

The console is cleared.

If I restore,

the two lines come back.

If I press start,

Nothing change because
the console is cleared

and then the strings are
displayed once again.

I now want a break line between
the two strings.

We will write
reaper. ShowConsoleMsg()

and set "\n" as parameters.

It is the code the make a line break.

As you can see, a break line has been put
between our two strings.

Instead of writing this
using several functions,

or should I say,
several times the ShowConsoleMsg function;

I could put all this in
one single function.

I could put all this at the same time.

That would give the following thing...

If I save + run,
it gives the same results as before.

Once again, I could add
other strings after that.

For exemple,
"I'm fine, thank you"

The break line hasn't been added,
I can add it

either here, at the beginiing, for exemple,

I can add it here,
the output is still the same,

or make just like before...

and all this output the same result.

Rather than use several time reaper.
ShowConsoleMsg which is long to write

and to add break lines everywhere,

I can create a function
that we will called Msg.

And which will have one parameter.

The function ends by "end",

and I write inside the declaration
what the function will do if we call it.

It will display that we
will put as parameters.

And it will add to this a breakline.

This means that,

if I call the function

and that I write a parameters in it

string in this case,

and string2

As, we can see here an error message

"reaper. ShowConsole is unknown"

I just forgot to add Msg
to the function name.

As you can see the line break
has been added automatically

I didn't have to rewrite it.

I duplicate this...

You can see that the break
line is added automatically,

and it is very faster to code.

The ShowConsoleMsg can accept numbers,

If I put 6,

You can see that the console output "6".

But if the variable value
we want to display doesn't exist,

for example, string3,

I will have an error message,
that will tell me

that I try to merge a nil
value with a string.

Nil is a type of value used in Lua,
that is used to define

that variable hasn't be declared
or that its value is nil.

For exemple, I will have the same result
if I put nil directly as parameter,

You can see a bug report message.

Same thing will occurs if string3...

had for value nil.

It is very important to avoid
this kind of message in a script,

It means that the scripts has bug,
it is not executed entirely.

In the case of our script,
to be sure that it works,

we will use a Lua native function
(not a REAPER special one)

which will convert in string
the parameter we put in it.

If I run the script again,
it display "nil" in plain text,

and there is no error anymore.

Our message function in then ready
to be used in our next script.