Return a unique temporary filename. This is an absolute pathname of a
file that does not exist at the time the call is made. No two calls
will return the same filename.
The module uses two global variables that tell it how to construct a
temporary name. The caller may assign values to them; by default they
are initialized at the first call to mktemp().
When set to a value other than None, this variable defines the
directory in which filenames returned by mktemp() reside.
The default is taken from the environment variable $TMPDIR; if
this is not set, either /usr/tmp is used (on Unix), or the
current working directory (all other systems). No check is made to
see whether its value is valid.
When set to a value other than None, this variable defines the
prefix of the final component of the filenames returned by
mktemp(). A string of decimal digits is added to generate
unique filenames. The default is either @pid. where
pid is the current process ID (on Unix), or tmp (all
other systems).
Warning: if a Unix process uses mktemp(), then
calls fork() and both parent and child continue to use
mktemp(), the processes will generate conflicting temporary
names. To resolve this, the child process should assign None to
template, to force recomputing the default on the next call
to mktemp().
