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OS2::REXX - access to DLLs with REXX calling convention and REXX runtime.


By default, the REXX variable pool is not available, neither to Perl, nor to external REXX functions. To enable it, you need to put your code inside REXX_call function. REXX functions which do not use variables may be usable even without REXX_call though.


        use OS2::REXX;
        $ydb = load OS2::REXX "ydbautil" or die "Cannot load: $!";
        @pid = $ydb->RxProcId();
        REXX_call {
          tie $s, OS2::REXX, "TEST";
          $s = 1;



        $dll = load OS2::REXX NAME [, WHERE];

NAME is DLL name, without path and extension.

Directories are searched WHERE first (list of dirs), then environment paths PERL5REXX, PERLREXX, PATH or, as last resort, OS/2-ish search is performed in default DLL path (without adding paths and extensions).

The DLL is not unloaded when the variable dies.

Returns DLL object reference, or undef on failure.

Define function prefix:


Define the prefix of external functions, prepended to the function names used within your program, when looking for the entries in the DLL.


                $dll = load OS2::REXX "RexxBase";

is the same as

                $dll = load OS2::REXX "RexxBase";

Define queue:


Define the name of the REXX queue passed to all external functions of this module. Defaults to "SESSION".

Check for functions (optional):

        BOOL = $dll->find(NAME [, NAME [, ...]]);

Returns true if all functions are available.

Call external REXX function:


Returns the return string if the return code is 0, else undef. Dies with error message if the function is not available.

Accessing REXX-runtime

While calling functions with REXX signature does not require the presence of the system REXX DLL, there are some actions which require REXX-runtime present. Among them is the access to REXX variables by name.

One enables REXX runtime by bracketing your code by

        REXX_call BLOCK;

(trailing semicolon required!) or

        REXX_call \&subroutine_name;

Inside such a call one has access to REXX variables (see below), and to

        REXX_eval EXPR;
        REXX_eval_with EXPR, 
                subroutine_name_in_REXX => \&Perl_subroutine

Bind scalar variable to REXX variable:

        tie $var, OS2::REXX, "NAME";

Bind array variable to REXX stem variable:

        tie @var, OS2::REXX, "NAME.";

Only scalar operations work so far. No array assignments, no array operations, ... FORGET IT.

Bind hash array variable to REXX stem variable:

        tie %var, OS2::REXX, "NAME.";

To access all visible REXX variables via hash array, bind to "";

No array assignments. No array operations, other than hash array operations. Just like the *dbm based implementations.

For the usual REXX stem variables, append a "." to the name, as shown above. If the hash key is part of the stem name, for example if you bind to "", you cannot use lower case in the stem part of the key and it is subject to character set restrictions.

Erase individual REXX variables (bound or not):

        OS2::REXX::drop("NAME" [, "NAME" [, ...]]);

Erase REXX variables with given stem (bound or not):

        OS2::REXX::dropall("STEM" [, "STEM" [, ...]]);


Note that while function and variable names are case insensitive in the REXX language, function names exported by a DLL and the REXX variables (as seen by Perl through the chosen API) are all case sensitive!

Most REXX DLLs export function names all upper case, but there are a few which export mixed case names (such as RxExtras). When trying to find the entry point, both exact case and all upper case are searched. If the DLL exports "RxNap", you have to specify the exact case, if it exports "RXOPEN", you can use any case.

To avoid interfering with subroutine names defined by Perl (DESTROY) or used within the REXX module (prefix, find), it is best to use mixed case and to avoid lowercase only or uppercase only names when calling REXX functions. Be consistent. The same function written in different ways results in different Perl stubs.

There is no REXX interpolation on variable names, so the REXX variable name TEST.ONE is not affected by some other REXX variable ONE. And it is not the same variable as!

You cannot call REXX functions which are not exported by the DLL. While most DLLs export all their functions, some, like RxFTP, export only "...LoadFuncs", which registers the functions within REXX only.

You cannot call 16-bit DLLs. The few interesting ones I found (FTP,NETB,APPC) do not export their functions.

I do not know whether the REXX API is reentrant with respect to exceptions (signals) when the REXX top-level exception handler is overridden. So unless you know better than I do, do not access REXX variables (probably tied to Perl variables) or call REXX functions which access REXX queues or REXX variables in signal handlers.

See t/rx*.t for examples.


Andreas Kaiser, with additions by Ilya Zakharevich