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=pod
=head1 NAME
RAND_load_file, RAND_write_file, RAND_file_name - PRNG seed file
=head1 SYNOPSIS
#include <openssl/rand.h>
int RAND_load_file(const char *filename, long max_bytes);
int RAND_write_file(const char *filename);
const char *RAND_file_name(char *buf, size_t num);
=head1 DESCRIPTION
RAND_load_file() reads a number of bytes from file B<filename> and
adds them to the PRNG. If B<max_bytes> is non-negative,
up to B<max_bytes> are read;
if B<max_bytes> is -1, the complete file is read.
Do not load the same file multiple times unless its contents have
been updated by RAND_write_file() between reads.
Also, note that B<filename> should be adequately protected so that an
attacker cannot replace or examine the contents.
If B<filename> is not a regular file, then user is considered to be
responsible for any side effects, e.g. non-anticipated blocking or
capture of controlling terminal.
RAND_write_file() writes a number of random bytes (currently 128) to
file B<filename> which can be used to initialize the PRNG by calling
RAND_load_file() in a later session.
RAND_file_name() generates a default path for the random seed
file. B<buf> points to a buffer of size B<num> in which to store the
filename.
On all systems, if the environment variable B<RANDFILE> is set, its
value will be used as the seed file name.
Otherwise, the file is called C<.rnd>, found in platform dependent locations:
=over 4
=item On Windows (in order of preference)
%HOME%, %USERPROFILE%, %SYSTEMROOT%, C:\
=item On VMS
SYS$LOGIN:
=item On all other systems
$HOME
=back
If C<$HOME> (on non-Windows and non-VMS system) is not set either, or
B<num> is too small for the path name, an error occurs.
=head1 RETURN VALUES
RAND_load_file() returns the number of bytes read or -1 on error.
RAND_write_file() returns the number of bytes written, or -1 if the
bytes written were generated without appropriate seeding.
RAND_file_name() returns a pointer to B<buf> on success, and NULL on
error.
=head1 SEE ALSO
L<RAND_add(3)>,
L<RAND_bytes(3)>,
L<RAND(7)>
=head1 COPYRIGHT
Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.
=cut
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