a sample which using openssl

main.c

#include <stdio.h>
#include <string.h>
#include "openssl/opensslv.h"
#include "openssl/sha.h"

void printBufferOfSha256(const unsigned char *output)
{
    int i = 0;
    for(; i < SHA256_DIGEST_LENGTH; i++) {
        printf("%02x", output[i]);
    }
    printf("\n");
}

void sha256(char *input, size_t inSize,  unsigned char hash[SHA256_DIGEST_LENGTH])
{
    SHA256_CTX sha256_context;
    SHA256_Init(&sha256_context);
    SHA256_Update(&sha256_context, input, inSize);
    SHA256_Final(hash, &sha256_context);
}

int main()
{
    printf("Using %s\n", OPENSSL_VERSION_TEXT);

    unsigned char hash[SHA256_DIGEST_LENGTH];
    const char *message = "hello";
    sha256((char *)message, strlen(message), hash);
    printBufferOfSha256(hash);
    return 0;
}