#include <stdio.h>	/* fprintf */#include <stdlib.h>	/* contains exit */#include <sys/types.h>	/* unistd.h needs this */#include <unistd.h>	/* contains read/write */#include <fcntl.h>#define MINIX_HEADER 32#define GCC_HEADER 1024void die(char * str){	fprintf(stderr,"%s\n",str);	exit(1);}void usage(void){	die("Usage: build boot system [> image]");}int main(int argc, char ** argv){	int i,c,id;	char buf[1024];	if (argc != 3)		usage();	for (i=0;i<sizeof buf; i++) buf[i]=0;	if ((id=open(argv[1],O_RDONLY,0))<0)		die("Unable to open 'boot'");	if (read(id,buf,MINIX_HEADER) != MINIX_HEADER)		die("Unable to read header of 'boot'");	if (((long *) buf)[0]!=0x04100301)		die("Non-Minix header of 'boot'");	if (((long *) buf)[1]!=MINIX_HEADER)		die("Non-Minix header of 'boot'");	if (((long *) buf)[3]!=0)		die("Illegal data segment in 'boot'");	if (((long *) buf)[4]!=0)		die("Illegal bss in 'boot'");	if (((long *) buf)[5] != 0)		die("Non-Minix header of 'boot'");	if (((long *) buf)[7] != 0)		die("Illegal symbol table in 'boot'");	i=read(id,buf,sizeof buf);	fprintf(stderr,"Boot sector %d bytes.\n",i);	if (i>510)		die("Boot block may not exceed 510 bytes");	buf[510]=0x55;	buf[511]=0xAA;	i=write(1,buf,512);	if (i!=512)		die("Write call failed");	close (id);		if ((id=open(argv[2],O_RDONLY,0))<0)		die("Unable to open 'system'");	if (read(id,buf,GCC_HEADER) != GCC_HEADER)		die("Unable to read header of 'system'");	if (((long *) buf)[5] != 0)		die("Non-GCC header of 'system'");	for (i=0 ; (c=read(id,buf,sizeof buf))>0 ; i+=c )		if (write(1,buf,c)!=c)			die("Write call failed");	close(id);	fprintf(stderr,"System %d bytes.\n",i);	return(0);}