RAND_load_file, RAND_write_file, RAND_file_name — PRNG seed file
char *RAND_file_name(char *buf, size_t num);
char *filename, long max_bytes);
RAND_file_name() generates a default path for the random seed
file. buf points to a buffer of size num in which
to store the filename. The seed file is $RANDFILE if that environment
variable is set, $HOME/.rnd otherwise. If $HOME is not set either,
or num is too small for the path name, an error
RAND_load_file() reads a number of bytes from file filename and
adds them to the PRNG. If max_bytes is non-negative,
up to to max_bytes are read; starting with
OpenSSL 0.9.5, if max_bytes is -1, the complete
file is read.
RAND_write_file() writes a number of random bytes (currently
1024) to file filename which can be used to initialize
the PRNG by calling RAND_load_file() in a later session.
RAND_load_file() returns the number of bytes read.
RAND_write_file() returns the number of bytes written, and
-1 if the bytes written were generated without appropriate seed.
RAND_file_name() returns a pointer to buf on
success, and NULL on error.
rand(3), RAND_add(3), RAND_cleanup(3)
RAND_load_file(), RAND_write_file() and RAND_file_name() are
available in all versions of SSLeay and OpenSSL.