#include	<sys/types.h>#include	<sys/stat.h>#include	<sys/mman.h>	/* mmap() */#include	<fcntl.h>#include	"ourhdr.h"#ifndef	MAP_FILE	/* 44BSD defines this & requires it to mmap files */#define	MAP_FILE	0	/* to compile under systems other than 44BSD */#endifintmain(int argc, char *argv[]){	int			fdin, fdout;	char		*src, *dst;	struct stat	statbuf;	if (argc != 3)		err_quit("usage: a.out <fromfile> <tofile>");	if ( (fdin = open(argv[1], O_RDONLY)) < 0)		err_sys("can't open %s for reading", argv[1]);	if ( (fdout = open(argv[2], O_RDWR | O_CREAT | O_TRUNC,												FILE_MODE)) < 0)		err_sys("can't creat %s for writing", argv[1]);	if (fstat(fdin, &statbuf) < 0)	/* need size of input file */		err_sys("fstat error");			/* set size of output file */	if (lseek(fdout, statbuf.st_size - 1, SEEK_SET) == -1)		err_sys("lseek error");	if (write(fdout, "", 1) != 1)		err_sys("write error");	if ( (src = mmap(0, statbuf.st_size, PROT_READ,					 MAP_FILE | MAP_SHARED, fdin, 0)) == (caddr_t) -1)		err_sys("mmap error for input");	if ( (dst = mmap(0, statbuf.st_size, PROT_READ | PROT_WRITE,					 MAP_FILE | MAP_SHARED, fdout, 0)) == (caddr_t) -1)		err_sys("mmap error for output");	memcpy(dst, src, statbuf.st_size);	/* does the file copy */	exit(0);}