1.4.1  High-Level Configuration

Now to the details: how to configure the I/O Restrictions (or get them out of your hair if you want them turned off).

1.4.1.1  Overall Options

1.4.1.1.1  No Restrictions
If this option is chosen, POV scripts can read/write everything (subject to operating system permission). The I/O Restriction system is turned off.
1.4.1.1.2  Restrict Write but Allow Read
If this option is chosen. POV scripts can read anything, but file creation and file write is only allowed in the specified directories (see Low-Level Configuration for more information on how to specify which directories).

Another way to put it is that I/O Restrictions are turned off for reading files, but not for writing them.

1.4.1.1.3  Restrict Read/Write
Both read and write by POV scripts is restricted to specified directories. Note that this is the default setting for a clean installation of POV-Ray for Unix v3.5.

1.4.1.2  Restrictions Affect all Core File I/O

Note that the above settings do not just affect scripted file I/O; they also affect things like include files, output files, and input .pov files. Basically any file-related input or output by the rendering engine. You should take careful note of this statement if you are in the habit of writing your output files to anywhere other than the same directory as the scene file is in (see below).

1.4.1.3  Additional Options

In addition to the above, there are two other options:
1.4.1.3.1  Permit Read/Write in Current Directory
If turned on, the current directory (but not any below it) is automatically added to the allowed list of read/write locations. For most people, this is a useful feature, so it is on by default for a clean install.

Please note that having this option turned off does not prevent read in the current directory if you have turned off read restrictions (as documented above), and nor will it prevent writing if you have turned off I/O Restrictions altogether. Also, turning it on will not allow read/write in subdirectories of the current directory - just that dir alone.

1.4.1.3.2  Disable Starting other Programs
If this option is selected (the default), shell-outs will not be permitted. 'Shell Outs' are a facility where an INI file can specify that a particular program be run either before or after a frame is rendered. If you want these, you have to explicitly allow them by unselecting this option.