prg12_6.c

配套光盘网络编程进程间的通信,网络编程进程间的通信是一本很经典的好书

#include <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/mman.h>

#define	FILE_MODE	(S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
#define	FILE	"test.data"
#define	SIZE	32768
int main(int argc,char **argv)
{
	int  fd,i;
	char  *ptr;
	fd = open(FILE,O_RDWR | O_CREAT | O_TRUNC,FILE_MODE);
	ptr = mmap(NULL,SIZE,PROT_READ | PROT_WRITE,MAP_SHARED,fd,0);
	
	for (i=4096;i<=SIZE;i+=4096)
	{
		printf("setting file size to %d\n",i);
		ftruncate(fd,i);
		printf("ptr[%d]=%d\n",i-1,ptr[i-1]);
	}
	exit(0);
}