bsplit/main.c

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

#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))

int main(int argc, char *argv[]) {
	for (int i = 1; i < argc; i++) {
		if (0==strcmp(argv[i], "-h") || 0==strcmp(argv[i], "--help")) {
			fprintf(stderr, "binary split\nArguments: file start end\nStart and end are byte indexes. End is optional\n");
			return 1;
		}
	}
	
	if (argc < 3) {
		fprintf(stderr, "Bad argc\n");
		return 1;
	}
	size_t pos = atol(argv[2]);
	
	size_t take = argc==4?atol(argv[3]):0;
	
	FILE * f = fopen(argv[1], "rb"); 
	fseek(f, pos, SEEK_SET);
	
#define CHUNKSZ 8192
	
	unsigned char chunk[CHUNKSZ];
	
	while (1) {
		size_t maxtake = take==0?CHUNKSZ : MIN(take, CHUNKSZ);
		size_t len = fread(chunk, 1, maxtake, f);
		if (errno != 0 || len == 0) {
			break;
		}
		
		fwrite(chunk, 1, len, stdout);
		
		if (take > 0) {
			take -= len;
			if (take == 0) break;
		}
	}	
	
	return 0;
}