hexadump.c

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

int main(int argc, char *argv[]) {
	FILE *fp;
	if (argc < 2) {
		fp = stdin;
	}
	else {
		fp = fopen(argv[1], "r");
		if (fp == NULL) {
			fprintf(stderr, "cannot open: %s\n", argv[1]);
			exit(1);
		}
	}
	
	char buf[BUFSIZ];
	size_t sz;
	int seq = 0;
	while ((sz = fread(buf, 1, BUFSIZ, fp)) != 0) {
		for (int i = 0; i < sz; i++) {
			if ((seq & 0x0f) == 0) {
				printf("%04X : ", seq);
			}
			printf("%02X ", buf[i] & 0xff);
			seq++;
			if ((seq & 0x0f) == 0) {
				putchar('\n');
			}
		}
	}
	putchar('\n');
	fflush(stdout);

	if (feof(fp)) {
		return 0;
	}
	else {
		return ferror(fp);
	}
}