Counts the occurrences of each byte in a file

byte_count.c

//
//  main.c
//  byte count
//
//  Created by kyle kersey on 11/16/14.
//  Copyright (c) 2014 kyle kersey. All rights reserved.
//

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>

int main(int argc, const char * argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: file name\n");
        return 0;
    }
    /* get size of file */
    struct stat st;
    stat(argv[1], &st);
    uint32_t file_size = st.st_size;
    
    /* allocate memory for file contents */
    unsigned char *file_contents;
    file_contents = malloc(file_size);
    
    /* open and read the file */
    FILE *fp = fopen(argv[1], "rb");
    if (fp == NULL) {
        fprintf(stderr, "cannot open file '%s'\n", argv[1]);
        return 0;
    }
    fread(file_contents, file_size, 1, fp);
    fclose(fp);
    
    /* array holding byte counts */
    uint32_t byte_list[0xFF];
    /* clear the array */
    memset(byte_list, 0, sizeof(byte_list));
    
    unsigned long file_index=0;
    while (file_index<file_size) {
        ++byte_list[file_contents[file_index++]];
    }
    
    int i;
    for (i=0; i<=0xFF; i++) {
        printf("%02X %d\n", i, byte_list[i]);
    }
    
    /* clear alocated memory */
    free(file_contents);
    
    return 0;
}