README_SAFE

This file explains the features of Regina that are disabled when Regina
is run in "restricted" mode.

Restricted mode is used in situations where you need to guarantee that
the author of a Rexx program is unable to affect the user's environment.
Situations where a restricted mode is applicable include, using Regina as
a database procedural language, or as language plugin for a Web browser.

Features of Regina that are disabled in restricted mode are:
  - LINEOUT, CHAROUT BIFs
  - POPEN BIF
  - "OPEN WRITE", "OPEN BOTH" subcommands of STREAM BIF
  - The "built-in" environments eg. SYSTEM, CMD or PATH of ADDRESS command
  - Setting the value of a variable in the external environment with
    VALUE BIF.
  - Calling external functions
  - RXFUNCADD BIF

To run Regina in restricted mode, you can start the Regina interpreter
from the command line with the '-r' switch, or when using the Rexx SAA API,
"ORing", RESTRICTED_REXX to the CallType parameter of RexxStart() function.