> On Jun 18, 2022, at 10:42 PM, ToddAndMargo via perl6-users
> <perl6-us...@perl.org> wrote:
>
> On 6/16/22 10:10, Rick Bychowski wrote:
>> sub MAIN($n = 20) {
>> .say for factors($n); # Nil
>> }
>
>
> I thought `MAIN` was a reserved variable. Am
> I missing something?
MAIN has a special meaning as a sub name; it declares a CLI (command-line
interface).
Just like this code declares a subroutine (that you can call within your
program) that expects two filenames and an optional flag :
sub do_it ( $file1, $file2, Bool :$dry-run ) {
...
}
, the same signature in a sub named "MAIN" declares that your whole script is
to be called on the command-line with two filenames and an optional flag :
sub MAIN ( $file1, $file2, Bool :$dry-run ) {
...
}
If I call that script like this:
./myscript.raku a.txt b.txt
, then MAIN gets 'a.txt' in $file1 and 'b.txt' in $file2. If I call it badly:
./myscript.raku a.txt b.txt c.txt
, then I get an error, with a usage message auto-generated by Raku:
myscript.raku [--dry-run] <file1> <file2>
For full details, see:
https://docs.raku.org/language/create-cli#index-entry-MAIN
--
Hope this helps,
Bruce Gray (Util of PerlMonks)
