Vim & Vision
[ #164 ] Blurring the Line between Modules and Scripts Permalink
Perl modules are named .pm and Perl scripts are .pl. You are supposed to keep your packages in your .pm and your scripts that you run from the command line in your .pl. However - you can create a (number of) package(s) within a .pl... and you can also run a .pm from the command line.
If you use a module then your module must be a .pm. If you require a module it can have any extension.
You could also have a script that is simply named yourapp without any file extension, which is useful for when you want to include your modules and script in the one file - presumably for easier distribution.
Keeping your modules as .pms and your scripts as .pls is nice for clarity - so people know by looking at a directory listing which file is which.
I've found that I sometimes want to treat one like the other, so that's what today's trick is all about.
First some background about how Python handles this.
Python files are just .pys, and if they contain a class or functions but also should be run by themselves like a script, then this idiom is used:
class Yours:
def something:
... code ...
def main:
... code ...
if __name__ == "__main__":
main()
We can emulate this in Perl like so:
package Yours;
sub something {
... code ...
}
package main;
sub main {
... code ...
}
&main if ! caller();
1;
This file could have any extension. If it is run as a script then main will be run - but if it is used or required then it won't be!
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