This manual entry describes the feature mechanism of Safe Tcl. It explains how features work and how to write and install new features. Features are installed into a Safe-Tcl interpreter by a security policy when the feature is allowed by the policy.
Command aliases execute code in the master interpreter when invoked in the slave interpreter.
For a discussion of multiple interpreters see the interp manual page included in the Tcl 8.0 distribution. If the install procedure generates an error, the interpreter executing the Tclet is killed, to prevent the Tclet from executing in a potentially unsafe undefined state. This ensures that the feature can be dynamically loaded as needed. Note that only the install procedure is required to be defined in this namespace. Other aspects of the implementation of the feature can be in other namespaces.