2024.2.20

1、用多进程完成两个文件的拷贝

#include<myhead.h>
int main(int argc, const char *argv[])
{
	pid_t pid=-1;
	FILE *fp=NULL;
	FILE *fp2=NULL;
	//打开文件
	if((fp=fopen(argv[1],"r"))==NULL)
	{
		perror("fopen error");
		return -1;
	}
	if((fp2=fopen(argv[2],"w"))==NULL)
	{
		perror("fopen error");
		return -1;
	}
	fseek(fp,0,SEEK_END);
	int len=ftell(fp);
	char buf[5]="";
	//创建一个子进程
	pid=fork();
	//判断父进程执行
	if( pid > 0 )
	{
		fseek(fp,0,SEEK_SET);
		while(1)
		{
			int res=fread(buf,1,sizeof(buf),fp);
			fwrite(buf,1,res,fp2);
			int len2=ftell(fp);
			if(len2>=len/2)
				break;
		}
	}
	else
	{
		fseek(fp,-len/2,SEEK_END);
		while(1)
		{
			int res=fread(buf,1,sizeof(buf),fp);
			fwrite(buf,1,res,fp2);
			if(res==0)
				break;
		}
		exit(EXIT_SUCCESS);   //会刷新缓冲区
	}

	//等待回收子进程
	wait(NULL);
	fclose(fp);
	fclose(fp2);


	return 0;
}