openssl_md5.c

#include <openssl/md5.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[]) {
  MD5_CTX c;

  unsigned char data[] = "your data";
  int len = strlen(data);
  unsigned char md5[MD5_DIGEST_LENGTH] = {0};

  MD5_Init(&c);
  MD5_Update(&c, data, len);
  MD5_Final(md5, &c);
  for (int i = 0; i < MD5_DIGEST_LENGTH; ++i)
    printf("%02x", md5[i]);

  puts("");

  return 0;
}