linux多進程拷貝文件

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

/*多進程拷貝文件*/
void sys_err(char* str)
{
	perror(str);
	exit(-1);
}

int main()
{
	pid_t pid;
	/*創建一個文件映射區*/
	//1.打開一個文件
	int fd;
	fd = open("bigdata.txt",O_RDWR|O_CREAT, 0644);
	if (fd == -1)
	{
		sys_err("open error\n");
	}
	//2.文件大小
	struct stat statbuf;
	stat("bigdata.txt", &statbuf);
	int size = statbuf.st_size;
	//3.mmap
	int* p;
	p = (int*)mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	if(p==MAP_FAILED)
		sys_err("mmap error\n");
	//5個進程負責拷貝的大小
	int unit_size = size / 5;
	int copy_size[5];
	for (int i = 0; i < 5; i++)
		copy_size[i] = unit_size;
	copy_size[4] = size - unit_size * 4;

	/*循環創建5個進程*/
	int* p_save = p;
	for (int j = 0; j < 5; j++)
	{
		pid = fork();
		if (pid > 0)
		{			
			fd = open("bigdata_copy.txt", O_CREAT|O_RDWR|O_APPEND, 0644);	
			write(fd, p, copy_size[j]);
			p_save += copy_size[j];
			p = p_save;
		}
		else if(pid==0)
			break;
		else if (pid < 0)
			sys_err("fork error\n");
	}
	printf("size:%d\n", size);
	munmap(p, size);
	return 0;
}
/*多進程拷貝文件*/