代码所用函数：open(),read(),write(),fstat(),lseek(),fork(),close();
#include <iostream>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
using namespace std;
int main(int argc,char* argv[])
{
if(argc < 4) {
cout << "Usage: ./a.out src des count_process" << endl;
return 0;
}
int srcfd = open(argv[1],O_RDONLY);
int desfd = open(argv[2],O_RDWR|O_CREAT|O_TRUNC,0664);
if(srcfd == -1 || desfd == -1) {
perror("open src or des error");
return -1;
}
struct stat statbuf;
int ret = fstat(srcfd,&statbuf);
if(ret == -1) {
perror("stat error");
return -1;
}
int fileSize = statbuf.st_size;
cout <<"fileSize = " <<fileSize<<endl;
int process_count = atoi(argv[3]);
int eachSize = fileSize/process_count;
cout <<"eachSize = " <<eachSize <<endl;
pid_t pid;
while(process_count--) {
pid = fork();
if(pid == -1) {
perror("fork error");
return -1;
} else if (pid == 0) {
break;
}
}
//拷贝工作全部由子进程完成
if(pid == 0) {
cout <<"process_count = " <<process_count<<endl;
//设置每个子进程对文件操作的偏移量
if(lseek(srcfd,eachSize*process_count,SEEK_SET) == -1 ||
lseek(desfd,eachSize*process_count,SEEK_SET) == -1) {
perror("lseek error");
return -1;
}
char buf[1024];
int flag = 0;
int readsize;
do{
readsize = read(srcfd,buf,sizeof(buf));
write(desfd,buf,readsize);
flag += readsize;
//最后创建出来的子进程负责最后一个文件块（这个块一般情况下都大于eachSize）
if(flag > eachSize && atoi(argv[3]) != process_count) {
break;
}
}while(readsize);
} else {
//回收一下子进程,此处就不回收了，由init进程代为回收
cout <<" i am parent" << endl;
}
if(close(srcfd) == -1 || close(desfd) == -1) {
perror("close error");
return -1;
}
return 0;
}
这种方式效率比较低，写文件时覆盖情况比较严重，欢迎指出代码问题。
