just returns the hash of argv[1]

sha1.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/sha.h>

/*
 * SHA1 Function
 * Description: just returns the hash of argv[1]
 * To compile: gcc -Wall sha1.c -o sha1 -lcrypto
 */

int main(int argc, char *argv[]) {
    char hash_string[SHA_DIGEST_LENGTH*2+1];
    unsigned char hash[SHA_DIGEST_LENGTH];
    if(argc!=2) {
        printf("Usage:\n./sha ARG\n");
        exit(1);
    }
    SHA_CTX ctx;
    SHA1_Init(&ctx);
    SHA1_Update(&ctx, argv[1], strlen(argv[1]));
    SHA1_Final(hash, &ctx);
    for (int i = 0; i < SHA_DIGEST_LENGTH; i++) {
        sprintf(&hash_string[i*2], "%02x", (unsigned int)hash[i]);
    }
    printf("Hash: %s\n", hash_string);
    return 0;
}