Description

   The tempnam function generates filenames for temporary files. It
   allows you to control the choice of a directory.

   If the directory argument is null or points to a string that is
   not a pathname for an appropriate directory, the pathname defined
   as P_tmpdir in the <stdio.h> header file is used. For programs
   running under a detached process, the directory argument cannot
   be null.

   You can bypass the selection of a pathname by providing the
   TMPDIR environment variable in the user environment. The value
   of the TMPDIR variable is a pathname for the desired temporary
   file directory.

   Use the prefix argument to specify a prefix of up to five
   characters for the temporary filename.

   The tempnam function returns a pointer to the generated pathname,
   suitable for use in a subsequent call to the free function.

   See also free.

                                  NOTE

      In contrast to tmpnam, tempnam does not have to generate
      a different filename on each call. tempnam generates a new
      filename only if the file with the specified name exists. If
      you need a unique filename on each call, use tmpnam instead
      of tempnam.