Test if a given file is JPEG or not in C

jpgtest.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_BYTES 3

int
main (const int argc, const char *argv[])
{
  if (argc != 2) {
    printf("usage: %s [filename]\n", argv[0]);
    return EXIT_FAILURE;
  }
  
  const char *filename = argv[1];
  
  FILE *fp = fopen(filename, "rb");
  if (fp == NULL) {
    perror("fopen");
    printf("error: unable to open the file\n");
    return EXIT_FAILURE;
  }
  
  char bytes[MAX_BYTES] = {0};
  char expected[MAX_BYTES] = {0xFF, 0xD8, 0xFF};
  
  int count = fread(bytes, 1, MAX_BYTES, fp);
  if (count != MAX_BYTES) {
    printf("error: unable to read the file\n");
    return EXIT_FAILURE;
  }
  
  if (memcmp(bytes, expected, MAX_BYTES) == 0) {
    printf("YES\n");
  }
  else {
    printf("NO\n");
  }
  
  return EXIT_SUCCESS;
}