char *tmpnam(char *s)
A pointer to a temporary/internal string buffer containing the temporary filename. Note that this string will be modified by further calls to tmpnam, so it should be regarded as a single use return value.
Generates a guaranteed unique filename that can be used to create a temporary file.
Note that the generated filename will contain directory path characters, ie it may be preceded by a backslash on Windows machines.
printf("A possible temporary filename: %s", tmpnam(NULL));