Temporary files

If all you're worried about is creating a temporary file, there are some handy helpers in C:

int mkstemp( template )
Generates unique temporary file name and opens file with O_EXCL and 0600 perms.

FILE* tmpfile()
Generates unique temporary file name and opens file with O_EXCL and 0600 perms
Immediately deletes file after creation.
More portable than mkstemp.

Functions not to use (vulnerable to race conditions)
char* tempnam( dir, prefix )
char* tmpnam( NULL )
char* mktemp( template )