Re: Problems with 'use lib'

When and where does $projectLocation get defined?

The "use lib" action is done at compile time, before statements like

  my $projectLocation = '/some/other/place';
[download]

can be executed to set the variable. You need to force your value to be defined during compilation. Perhaps this might be more like what you were thinking?

BEGIN {
  my $projectLocation = '/some/other/place';
  use lib $projectLocation;
}
[download]

But then this gets back to something like the starting question - where does the value for $projectLocation come from? Ah, an environment variable. So maybe

BEGIN {
  use lib $ENV{MYLIBRARYDIR};
  printf "in BEGIN:   '%s'\n", join("', '", @INC );
}
[download]

will do what you want.

Comment on Re: Problems with 'use lib' Select or Download Code

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Re: Re: Problems with 'use lib' by esh (Pilgrim) on Aug 21, 2003 at 07:38 UTC
I don't think this code will do what you want: `BEGIN { my $projectLocation = '/some/other/place'; use lib $projectLocation; }` [download] The "use lib" inside the BEGIN block will be executed before the assignment since it is also inside the BEGIN block. Try this instead: `my $projectLocation; BEGIN { $projectLocation = '/some/other/place'; } use lib $projectLocation;` [download] The "use" is like another BEGIN so these two pieces of code will be executed in sequence now. -- Eric Hammond	[reply] [d/l] [select]
Re: Re: Re: Problems with 'use lib' by shenme (Priest) on Aug 21, 2003 at 18:02 UTC
I was going to say that wasn't true, but went back and looked at the last test program I was using and decided I hadn't tested that situation correctly. Using code `BEGIN { my $foo = 'foom'; use lib $foo; }` [download] results in error messages Use of uninitialized value in string eq at /usr/lib/perl5/5.8.0/i386-linux-thread-multi/lib.pm line 29. Empty compile time value given to use lib at hotshot.pl line 5 Using your code `my $foo; BEGIN { $foo = 'foom'; } use lib $foo; printf "executing: '%s'\n", join("', '", @INC );` [download] returns the desired results executing: 'foom', '/usr/lib/perl5/5.8.0/i386-linux-thread-multi', ... , '.' Just to try something different I tried `BEGIN { our $foo = 'foom'; } use lib $foo;` [download] which also worked. Another thing to put in the list of things to re-study. Key is that "use" (and other pragmas?) are executed (at compile time) before surrounding code at the same apparent 'level'. By enclosing code in a BEGIN block ahead of the "use" we force it into compile time execution before the following "use" is executed. (Or something like that ;-)	[reply] [d/l] [select]


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