Practical Programming in Tcl & Tk, Third Edition

I/O from Safe Interpreters

A safe child interpreter cannot open files or network sockets directly. An alias can create an I/O channel (i.e., open a file or socket) and give the child access to it. The parent can share the I/O channel with the child, or it can transfer the I/O channel to the child. If the channel is shared, both the parent and the child can use it. If the channel is transferred, the parent no longer has access to the channel. In general, transferring an I/O channel is simpler, but sharing an I/O channel gives the parent more control over an unsafe child. The differences are illustrated in Example 19-7 and Example 19-9.

There are three properties of I/O channels that are important to consider when choosing between sharing and transferring: ...