DEV02 - Extending Applications with REXX

Christian Langanke for netlabs.org

Overview

• Script Language REXX
• REXX integration in eComStation
• Extending REXX with external libraries
• Extending Applications with REXX
• More advanced Extensions to REXX

Script Language REXX

• Interpreted Programming Language
• Classic REXX is part of OS/2 1.2 and newer
• Object Oriented REXX (OOREXX) superseeds Classic REXX
  • part of OS/2 Warp 4 and better
  • not active by default, switch with switchrx.cmd and reboot
  • mostly compatible to Classic REXX (minor incompatibility in few functions
• Exists for other platforms such as MVS, AIX, Windows, Linux
• OOREXX is Open Source (see www.oorexx.org)
• Alternative implementations: e.g. Regina REXX

REXX integration in eComStation

• Integration by Command Processor CMD.EXE
• Batch files with Comment Header are passed to REXX interpreter
• Tokenized version of scripts stored as extended attributes
• Set of system-near APIs available as Sys* REXX function library
• several Sys-APIs for creating, deleting and modifying Workplace Shell Objects

Extending REXX - External Libraries

• external functions loadable via DLL interface
• prominent sample: REXXUTIL.DLL with Sys* function
• load DLL with RxFuncAdd
• call added functions like internal REXX functions
• many external DLLs available, see overview in INF file of REXX Tips and Tricks
• external code accesses the REXX Variable Pool via RexxVariablePool
  • read values from/ pass values to REXX Script

Extending Applications with REXX 1/3

• REXX interpreter is called by applications with RexxStart
• Applications may provide a context, which can be selected by REXX function ADDRESS
  • REXX Commands not resolved or explicitely put in quotes are passed to the application context
  • Example: eComStation Commands to the Command Processor CMD.EXE, defining the context CMD

Extending Applications with REXX 2/3

• Applications add variables to or read variales from the REXX variable pool by
  • registering an exit handler for the initialization with RexxRegisterExitExe/Dll
  • within the handler add values to the variable pool with RexxVariablePool
• Example: Script Engine of Wireless LAN Monitor
  • script is called on events like connect and disonnect
  • variables like network name and TCP/IP configuration values are passed to the script

Extending Applications with REXX 3/3

• Applications register a subcommand handler with RexxRegisterSubcomExe/Dll to establish a context.
• Example: DFSee
  • script is called by DFSee - specified on commandline
  • Context name is DFS
  • DFSee related commands are included in the REXX script and passed to the subcommand handler of DFSee

More advanced Extensions to REXX

• Create REXX Queues from external code and exchange data by these
• add REXX functions to the Macro Space
• Register a System Exit handler with RexxRegisterExitExe/Dll to intercept
  • initialization or termination of REXX interpreter
  • call of external functions
  • textmode input and output
  • access to external data queues
  • REXX events like HALT or TRACE

The End

Thank you very much for your your attention!