IO和进程（进程）

今日任务

代码：

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

/*
 * function:    复制图片
 * @param [ in] 
 * @param [out] 
 * @return      
 */

int main(int argc, const char *argv[])
{
	//打开文件
	int fd=open("./DSCN7970.JPG",O_RDONLY);
	if(fd==-1){
		puts("fd open failed");
		return -1;
	}
	int dest=open("./copy.JPG",O_WRONLY|O_CREAT|O_TRUNC,0664);
	if(dest==-1){
		puts("dest open failed");
		return -1;
	}

	//创建子进程，父进程拷贝前一半，子进程拷贝后一半
	int size=lseek(fd,0,SEEK_END);//获取总字节大小
	printf("size=%d\n",size);
	pid_t pid=fork();
	char c;
	//父进程
	if(pid>0){
		wait(NULL);
		lseek(fd,0,SEEK_SET);
		lseek(dest,0,SEEK_SET);

		puts("parent process copy start");
		for (int i=0; i<size/2; i++)
		{
			read(fd,&c,1);
			write(dest,&c,1);
		}
		puts("parent process copy end");
	}
	else if(pid==0){
		lseek(fd,size/2,SEEK_SET);
		lseek(dest,size/2,SEEK_SET);
		puts("son process copy start");
		for (int i=size/2; i<size; i++)
		{
			read(fd,&c,1);
			write(dest,&c,1);
		}
		puts("son process copy end");
	}else{
		perror("fork");
		return -1;
	}
	puts("copy success");

	//关闭文件
	close(dest);
	close(fd);
	return 0;
}

今日思维