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Re^2: [implementation specific to windows] writing a proper batch file for terminal start-up

by Aldebaran (Chaplain)
on Oct 17, 2019 at 16:33 UTC ( #11107611=note: print w/replies, xml ) Need Help??


in reply to Re: [implementation specific to windows] writing a proper batch file for terminal start-up
in thread [implementation specific to windows] writing a proper batch file for terminal start-up

If you have your code set up as a standard directory structure, e.g. with the script in ./bin and any modules under ./lib, then you can use libraries like rlib to add the relative paths in your calling script.

Ok, this is helpful and worth exploring. I must say, however, that I'm unable to follow what rlib is doing. Let's look at the source:

package rlib; use strict; use vars qw($VERSION @ISA); use lib (); use File::Basename qw(dirname); use File::Spec; $VERSION = "0.02"; @ISA = qw(lib); sub _dirs { my($pkg,$file) = (caller(1))[0,1]; my @rel = @_ ? @_ : qw(../lib lib); my $dir; # if called from package main then assume we were called # by a script not a module if($pkg eq 'main') { require FindBin; # hide "used only once" warning $dir = ($FindBin::Bin,$FindBin::Bin)[0]; } else { require Cwd; $dir = Cwd::abs_path(dirname($file)); } # If we were called by a package then traverse upwards # to root of lib while($pkg =~ /::/g) { $dir = dirname($dir); } if($^O eq 'VMS') { require VMS::Filespec; @rel = map { VMS::Filespec::unixify($_) } @rel; } map { File::Spec->catdir($dir,$_) } @rel; } sub import { shift->SUPER::import( _dirs(@_) ); } sub unimport { shift->SUPER::unimport( _dirs(@_) ); } 1; __END__

I fail to see how _dirs is populated. Can someone talk through how this works? In particular, I do not understand the syntax of the following lines:

my($pkg,$file) = (caller(1))[0,1]; my @rel = @_ ? @_ : qw(../lib lib);

and

while($pkg =~ /::/g) {

How might I test this? Thx for your comments,

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Re^3: [implementation specific to windows] writing a proper batch file for terminal start-up
by swl (Deacon) on Oct 17, 2019 at 20:36 UTC

    The caller line gets the name of the package and file that called the use rlib. If you use caller with no arguments then it tells you about the sub it is called from, but in this case the argument tells it to go one higher in the call stack. See the docs for caller for more details.

    The second line is simply setting default arguments using the ternary operator. If the arguments array @_ is empty then it will add ../lib and lib to @INC, otherwise it will work with the passed arguments.

    The while loop is for cases where use rlib is called from a package like Some::Package::PP. In that case it will try to find the ancestral lib dir. It assumes caller(1) will return a file name something like /somepath/lib/Some/Package/PP.pm. The =~ /::/g will return an array of how many times the package name includes ::, and will go up that many directories to find /somepath/lib/Some. This means it will eventually add /somepath/lib/Some/../lib and /somepath/lib/Some/lib to @INC (I might be off by one on the dirs, as I have not tested, but the principle is the same).

    To test the while line:

    # on windows - update quotes as needed perl -E"my $x = q|Some::Package::PP|; say 1 while $x =~ /::/g" #produces 1 1
Re^3: [implementation specific to windows] writing a proper batch file for terminal start-up
by Anonymous Monk on Oct 17, 2019 at 23:48 UTC

    I fail to see how _dirs is populated. Can someone talk through how this works? In particular, I do not understand the syntax of the following lines:

    :) Basic debugging checklist

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