RAND_load_file.3ssl man page

RAND_load_file, RAND_write_file, RAND_file_name — PRNG seed file


 #include <openssl/rand.h>

 const char *RAND_file_name(char *buf, size_t num);

 int RAND_load_file(const char *filename, long max_bytes);

 int RAND_write_file(const char *filename);


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.

On all systems, if the environment variable RANDFILE is set, its value will be used as the seed file name.

Otherwise, the file is called ".rnd", found in platform dependent locations:

On Windows (in order of preference)




On all other systems


If $HOME (on non-Windows and non-VMS system) is not set either, or num is too small for the path name, an error occurs.

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 max_bytes are read; 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.

Return Values

RAND_load_file() returns the number of bytes read or -1 on error.

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.

See Also

rand(3), RAND_add(3), RAND_cleanup(3)

Referenced By

mailx(1), rand.3ssl(3), RAND_add.3ssl(3).

2017-11-02 1.1.0g OpenSSL