1> 使用多个进程实现文件拷贝

#include<myhead.h>
int main(int argc, const char *argv[])
{pid_t pid;pid=fork();int fdr;char buf;if((fdr=open(argv[1],O_RDONLY))==-1){perror("open error");return -1;}int len=lseek(fdr,0,SEEK_END)-lseek(fdr,0,SEEK_SET);int num=len/2;if(pid>0){int num1,fdw;num1=0;if((fdw=open(argv[2],O_WRONLY|O_CREAT|O_TRUNC,0664))==-1){perror("open error");return -1;}lseek(fdr,0,SEEK_SET);while(num1<num){int res=read(fdr,&buf,sizeof(buf));write(fdw,&buf,res);num1+=res;}close(fdw);}else if(pid==0){int fdw;if((fdw=open(argv[2],O_WRONLY|O_CREAT|O_APPEND,0664))==-1){perror("open error");return -1;}lseek(fdr,len-num-1,SEEK_SET);lseek(fdw,0,SEEK_END);int res;while((res=read(fdr,&buf,sizeof(buf)))>0){write(fdw,&buf,res);}close(fdw);}close(fdr);return 0;
}