Re: How to set LD_LIBRARY_PATH

On 2010-05-31 15:52:21 +0200, Peter J. Holzer wrote:
> On Linux (at least i386[1]) the loader uses the current value of
> LD_LIBRARY_PATH when it is asked to load an .so file. So you can change
> LD_LIBRARY_PATH just before you want to load the library. 
> 
> On Solaris the loader uses the value of LD_LIBRARY_PATH at program
> startup. Changing LD_LIBRARY_PATH during runtime has no effect on the
> process itself, just its children. I don't know why this is the case,
> but I guess that LD_LIBRARY_PATH is split into components when the first
> library (probably libc) and after that the components aren't used any
> more.
> 
>         hp
> 
> 
> [1] I seem to remember that I ran into problems either on x86_64 or on
>     power, but I don't remember the details. If it's x86_64, I should be
>     able to test it (don't have access to power-based systems any more).

Just for the record: That problem does exist on Linux/x86_64.

I just ran into the issue moving a bunch of CGI scripts from a
Linux/i386 box to a Linux/x86_64 box. 

They do something like:

    if (open(E, "$offl_root/dbi/env")) {
        while (<E>) {
            chomp;
            my ($k, $v) = split(/=/);
            $ENV{$k} = $v; 
            printlog('DEBUG', "setting $k=$v");
        }
    }   
    my ($data_source, $username, $auth) = read_cred("$offl_root/dbi/usradm");

    my $dbh;
    eval {
        $dbh = DBI->connect($data_source, $username, $auth,
                            { AutoCommit => 0,
                              PrintError => 1,  
                              RaiseError => 1
                            }
                           );
    };  
    if ($@) {
        ...
    }

where $offl_root/dbi/env contains several environment variables, among
them ORACLE_HOME and LD_LIBRARY_PATH. 

On Linux/i386 this works fine. On Linux/x86_64 it fails with the error
message

connection to dbi:Oracle:wpdb.wsr.ac.at as usradm failed:
install_driver(Oracle) failed: Can't load
'/usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi/auto/DBD/Oracle/Oracle.so'
for module DBD::Oracle: libocci.so.10.1: cannot open shared object file:
No such file or directory at
/usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi/DynaLoader.pm line 230.

despite the fact that libocci.so.10.1 is in the LD_LIBRARY_PATH.

If I set LD_LIBRARY_PATH in the Apache config, it works as expected. 

So I conclude that Linux/x86_64, like Solaris, but unlike Linux/i386,
ignores changes to LD_LIBRARY_PATH after a program is started.

        hp



-- 
   _  | Peter J. Holzer    | Auf jedem Computer sollte der Satz Ludwigs II
|_|_) | Sysadmin WSR       | eingeprägt stehen: "Ein ewig Rätsel will ich
| |   | [email protected]      | bleiben, mir und andern."
__/   | http://www.hjp.at/ |    -- Wolfram Heinrich in desd

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