linux c md5 文件

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

void compute_md5(const char *filename, unsigned char digest[16]) {
    FILE *file;
    MD5_CTX ctx;
    unsigned char buffer[1024];
    size_t bytes;

    if ((file = fopen(filename, "rb")) == NULL) {
        perror("Unable to open file");
        return;
    }

    MD5_Init(&ctx);
    while ((bytes = fread(buffer, 1, sizeof(buffer), file)) != 0)
        MD5_Update(&ctx, buffer, bytes);
    MD5_Final(digest, &ctx);

    fclose(file);
}

int main(int argc, char **argv) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
        return 1;
    }

    unsigned char digest[16];
    compute_md5(argv[1], digest);

    char md5string[33];
    for (int i = 0; i < 16; ++i)
        sprintf(&md5string[i*2], "%02x", (unsigned int)digest[i]);

    printf("MD5 of '%s' is: %s\n", argv[1], md5string);
    return 0;
}

gcc -o md5_example md5_example.c -lssl -lcrypto

./md5_example yourfile.txt