程序代码：

#include <stdio.h>
#include "openssl/bio.h"
#include "openssl/rand.h"

int main(void)
{
  char buf[20], *p;
  unsigned char out[20], filename[50];
  int ret, len;
  BIO *print;

  RAND_screen();
  strcpy(buf, "我的随机数");
  RAND_ADD(buf, 20, strlen(buf));
  strcpy(buf, "23424d");
  RAND_seed(buf, 20);

  while(1)
    {
      ret = RAND_status();
      if(ret == 1)
    {
      printf("seeded enouth!\n");
      break;
    }
      else
    {
      printf("not enough sedded!\n");
      RAND_pool();
    }
    }

  p = RAND_file_name(filename, 50);
  if (p == NULL)
    {
      printf("can not get rand file\n");
      return -1;
    }

  ret = RAND_write_file(p);
  len = RAND_load_file(p ,1024);
  ret = RAND_bytes(out, 20);

  if (ret != 1)
    {
      printf("err.\n");
      return -1;
    }

  print = BIO_new(BIO_s_file());
  BIO_set_fp(print, stdout, BIO_BICLOSE);
  BIO_write(print, out, 20);
  BIO_write(print, "\n",2);
  BIO_free(print);
  RAND_cleanup();
 

  return 0;
}

程序代码：

root@zjs-bigtree:~# ldd /usr/bin/openssl
    linux-gate.so.1 =>  (0xb7734000)
    libssl.so.1.0.0 => /lib/i386-linux-gnu/libssl.so.1.0.0 (0xb76cb000)
    libcrypto.so.1.0.0 => /lib/i386-linux-gnu/libcrypto.so.1.0.0 (0xb7520000)
    libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7376000)
    libdl.so.2 => /lib/i386-linux-gnu/libdl.so.2 (0xb7371000)
    libz.so.1 => /lib/i386-linux-gnu/libz.so.1 (0xb735b000)
    /lib/ld-linux.so.2 (0xb7735000)

~/test/openssl/nine/rand $ gcc rand.c -L/lib/i386-linux-gnu -Icrypto -o rand
rand.c:2:25: 致命错误： openssl/bio.h：没有那个文件或目录
编译中断。