display file in hex

hex.c

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


int main (int argc, char * argv[]) {

    int filesize;
    int i;
    unsigned char byte;
    char string[41];
    FILE * fh;
    
    if (argc != 2) {
        fprintf(stderr, "%s <filename>\n", argv[0]);
        exit(0);
    }
    
    fh = fopen(argv[1], "rb");
    
    fseek(fh, 0, SEEK_END);
    filesize = (int) ftell(fh);
    fseek(fh, 0, SEEK_SET);
    
    i = 0;
    while (fread(&byte, 1, 1, fh)) {
        if (i % 32 == 0)
            printf("[%08x]   ", i);
        printf("%02x", byte);
        if ((byte >= 0x20) && (byte < 0x7f))
            string[i%32] = byte;
        else
            string[i%32] = '.';
        string[(i%32) + 1] = 0;
        i++;
        if (i % 32 == 0)
            printf("   %s\n", string);
        else if (i % 4 == 0)
            printf(" ");
    }
    
    if (i > 0) {
        for (; i % 32 != 0; i++) {
            if (i % 4 == 0)
                printf("   ");
            else
                printf("  ");
        }
        printf("   %s\n", string);
    }
    else
        printf("\n");
    
    fclose(fh);
    
    return 0;

}