Create a file with a randomly generated name and return the opened
stream. The resulting pathname is generated from TEMPLATE, which
is a string representing a pathname template. A percent sign (%)
in that string is replaced by a randomly generated string to make
the filename unique. The default for TEMPLATE places temporary
files in the TEMPORARY-FILES logical pathname host, which is
automatically set up in a system specific manner. The file name
generated from TEMPLATE is merged with *DEFAULT-PATHNAME-DEFAULTS*,
so random pathnames relative to that directory can be generated by
not specifying a directory in TEMPLATE.
GENERATE-RANDOM-STRING can be passed to override the default
function that generates the random name component. It should
return a random string consisting of characters that are permitted
in a pathname (logical or physical, depending on TEMPLATE).
The name of the temporary file can be accessed calling the PATHNAME
function on STREAM. For convenience, the temporary file is opened
on the physical pathname, i.e. if the TEMPLATE designate a logical
pathname the translation to a physical pathname is performed before
opening the stream.
In order to create a unique file name, OPEN-TEMPORARY may loop
internally up to MAX-TRIES times before giving up and signalling a