This option, if present, specifies the directory to be used for temporary files.
This has a double function: firstly and most straightforwardly, it indicates where temporary files should be created if, for some reason, the default location is unsuitable; secondly, if the script finds there a file (from a previous run) which it was about to generate, it does not regenerate it, but instead simply reuses it. The first function may be useful in some circumstances; the second is primarily a debugging facility, is subtle, and its use is discouraged.
Type: string; default: generated