jrw has asked for the wisdom of the Perl Monks concerning the following question:

On Linux (currently testing RHEL6.5), it appears that LD_LIBRARY_PATH must be defined/exported *outside* my script in order to load DBD::Oracle successfully. This is not so on AIX (LIBPATH), and I wasn't expecting it on Linux either. Setting $ENV{LD_LIBRARY_PATH} in a BEGIN block at the top of my script gets the standard 
install_driver(Oracle) failed: Can't load '/home/jrw/perl_dbi/linux/li
+b/perl5/x86_64-linux-thread-multi/auto/DBD/Oracle/Oracle.so' for modu
+le DBD::Oracle: libclntsh.so.18.1: cannot open shared object file: No
+ such file or directory at /usr/lib64/perl5/DynaLoader.pm line 200.
 at (eval 38) line 3

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whereas exporting LD_LIBRARY_PATH *before* running perl -e allows the script to succeed. Does DynaLoader cache the initial LD_LIBRARY_PATH during script startup? Or is something else going on? Test script: 
export DIR=/home/jrw/perl_dbi/linux

unset LD_LIBRARY_PATH
# export LD_LIBRARY_PATH=$DIR/oracle_instantclient

perl -e '
   use strict;
   use warnings;
   BEGIN { $ENV{LD_LIBRARY_PATH} = "$ENV{DIR}/oracle_instantclient" }
   use lib "$ENV{DIR}/lib/perl5";
   use DBI;

   my @drivers = DBI->available_drivers;
   print "Drivers = @drivers\n";
   foreach my $driver (@drivers) {
      my @databases = DBI->data_sources($driver);
      print "   Driver: $driver, data sources = @databases\n";
   }
'

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Replies are listed 'Best First'.
Re: Why must LD_LIBRARY_PATH be defined outside script for DBD::Oracle?
by syphilis (Archbishop) on Jul 27, 2019 at 00:07 UTC
    BEGIN { $ENV{LD_LIBRARY_PATH} = "$ENV{DIR}/oracle_instantclient" }

    Has $ENV{DIR} been set correctly ?
    I would include, inside that BEGIN{} block, a check to verify that $ENV{LD_LIBRARY_PATH} has in fact been set to its expected value - and have the script die() if the check fails.

    Cheers,
    Rob
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Re: Why must LD_LIBRARY_PATH be defined outside script for DBD::Oracle?
by Anonymous Monk on Jul 26, 2019 at 00:32 UTC
    Its a hack
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[reply]
        I'm well aware of the evils of LD_LIBRARY_PATH. But that was not my question, which was: why does Perl on Linux seem to require that LD_LIBRARY_PATH be defined before the script starts rather than being defined in a BEGIN block before DBD is loaded?

        P.S. If anyone can tell me how to do the equivalent of setting rpath in the .so files produced by AIX's xlc compiler, then I could go that route. But since I currently have to set LIBPATH for AIX (which I can set *inside* the script as opposed to prior to running the script like I have to do on Linux), then I'll stick to trying to set LD_LIBRARY_PATH on Linux.

[reply]
[d/l]

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