验证wait和文件IO拷贝

若没有子进程wait函数是否阻塞，wait函数是否运行成功.

#include <head.h>
int main(int argc, const char *argv[])
{
	pid_t wpid=wait(NULL);
	printf("wpid=%d __%d__\n",wpid,__LINE__);
	printf("pid=%d __%d__\n",getpid(),__LINE__);
	return 0;
} 

用文件IO函数拷贝一张图片，要求子进程拷贝后半部分，父进程拷贝前半部分。

#include <head.h>
int main(int argc, const char *argv[])
{
	int fp=open("./1.jpg",O_RDONLY);
	if(fp<0)
	{
		perror("open");
		return -1;
	}
	off_t size=lseek(fp,0,SEEK_END);
	printf("size=%ld\n",size);
	int cp=open("./2.jpg",O_RDWR|O_CREAT|O_TRUNC,0777);
	if(cp<0)
	{
		perror("open");
		return -1;
	}
	pid_t pid=fork();
	char buf[1]="";
	ssize_t res=0;
	lseek(fp,0,SEEK_SET);
if(pid>0)
	{
		wait(NULL);
		lseek(fp,0,SEEK_SET);
		lseek(cp,0,SEEK_SET);
		while(1)
		{						
			ssize_t d=lseek(fp,0,SEEK_CUR);
			if(d==(size/2))
			break;
			bzero(buf,sizeof(buf));	
			res=read(fp,buf,sizeof(buf));
			write(cp,buf,res);
		}
	}
else if(pid==0)
	{
		ssize_t a=lseek(fp,(size/2),SEEK_SET);
		lseek(cp,(size/2),SEEK_SET);
		printf("a=%ld\n",a);
		while(1)
		{
			bzero(buf,sizeof(buf));
			res=read(fp,buf,sizeof(buf));
			if(res==0)
				break;
			write(cp,buf,res);
		}
	exit(0);	
	}
	else
	{
		perror("fork");
		return -1;
	}
	close(cp);
	close(fp);
	return 0;
}