多进程拷贝

多进程拷贝：实现将文件内容拷贝给另一个文件

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

#define BUF_SIZE 400

int main(int argc, char *argv[])
{
	int fd1, fd2, ret, len, i, n;
	char *src = NULL;
	char *dest = NULL;
	pid_t pid;

	printf("Current file path:%s\n", argv[0]);

	fd1 = open(argv[1], O_RDWR);
	if(fd1 == -1)
	{
		perror("open mmap.txt error:");
		exit(1);
	}
	printf("mmap文件打开成功\n");

	len = lseek(fd1, 0, SEEK_END);
	printf("len = %d\n", len);

	//将文件分为n个部分,创建n个子进程
	if(len % BUF_SIZE == 0)//为BUF_SIZE的整数倍
	{
		n = len / BUF_SIZE;
		printf("n = %d\n", n);
	}
	else//不是BUF_SIZE的整数倍,加一个子进程
	{
		n = len / BUF_SIZE + 1;
		printf("n = %d\n", n);
	}


	lseek(fd1, 0, SEEK_SET);

	src = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, fd1, 0);
	if(src == MAP_FAILED)
	{
		perror("mmap mmap.txt error:");
		exit(1);
	}
	printf("src mmap映射区创建成功\n");
	//创建完共享内存后既可以关闭文件描述符
	close(fd1);

	fd2 = open(argv[2], O_RDWR|O_CREAT, 0664);
	if(fd2 == -1)
	{
		perror("open copy.txt error:");
		exit(1);
	}
	printf("copy文件打开成功\n");

	//为目标文件拓展上面返回的文件描述符指向文件的大小
	ret = ftruncate(fd2, len);
	if(ret == -1)
	{
		perror("ftruncate error:");
		exit(1);
	}

	dest = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, fd2, 0);
	if(dest == MAP_FAILED)
	{
		perror("mmap copy.txt error:");
		exit(1);
	}
	printf("dest mmap映射区创建成功\n");
	//创建完共享内存后既可以关闭文件描述符
	close(fd2);

	for(i = 0; i < n; i++)
	{
		pid = fork();

		if(pid < 0)
		{
			perror("fork error:");
			exit(1);
		}
		else if(pid == 0)
		{
			break;
		}
	}

	if(i < n)
	{
		//sleep(i);
		//printf("I'm %dth child, I'm copying...\n", getpid());
		//从第 i 个字符开始复制，连续复制 BUF_SIZE 个字符
		if(i == (n - 1))
		{
			memcpy(dest + i*BUF_SIZE,src + i*BUF_SIZE, (len - i*BUF_SIZE));
			//printf("Last child %d process print data:%s\n", getpid(), dest);
			printf("Last i's length:%d\n", (len - i*BUF_SIZE));
		}
		else
		{
			memcpy(dest + i*BUF_SIZE,src + i*BUF_SIZE, BUF_SIZE);
			//printf("Child %d process print data:%s\n", getpid(), dest);
		}

	}
	else
	{
		//sleep(i);
		wait(NULL);
		printf("拷贝结束!\n");

		ret = munmap(src, len);
		if(ret == -1){
			perror("munmap src error:");
			exit(1);
		}

		ret = munmap(dest, len);
		if(ret == -1){
			perror("munmap dest error:");
			exit(1);
		}
	}

	return 0;
}

 

来源：CSDN

作者：allan-xy

链接：https://blog.csdn.net/tiandaochouqingong/article/details/103808990