Autohotkey / AHK - Param %1% not accessible within a function

Question

I'm having a problem with accessing the %1% ( Startup Param that has been passed to the Script by the console ) in Autohotkey.

When I use the following code (outside of a function):

Msgbox %1%

I get the output of the Param that has been passed to the Script. But as soon as I use the following Code:

HelloWorld() {
    Msgbox %1% 
}
HelloWorld()

The output is empty.

I also tried to assign %1% to a global variable, or to pass it to the Function as a parameter but it didn't work for me neither.

Thank you

Answer 1

I believe the command line parameter variables are considered global variables, so in order to use them in a non-expression context inside a function you have to declare them as global:

HelloWorld() {
    global 1
    Msgbox %1% 
}
HelloWorld()

It gets even more confusing once you want to use them in expressions (such as using % in the text argument for MsgBox), since they will be treated as numbers so you have to indirectly access them through variables:

HelloWorld() {
    ;global 1
    ; Neither of these two expressions access the variable named "1"
    ;Msgbox % 1
    ;Msgbox % %1%

    ; You have to do this instead:
    p := 1
    MsgBox % %p% ; p is translated to 1 and then "1" is used as a variable name
}
HelloWorld()

Note that doing this doesn't require global 1.

If you're using the newest version of AHK, you instead probably want to use the newly introduced built-in variable A_Args, which is an array that holds the command line parameters. Being built-in, it doesn't have to be declared global, and it ultimately makes the code clearer:

HelloWorld() {
    MsgBox % "Number of command line args received: " A_Args.Length() "`n"
             . "First argument: " A_Args[1]
}
HelloWorld()