//by mmap multi-process copy files 
//
//
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  


using namespace std; 

Int main (int arg c, char * argv []) 
{
If (arg c! 
=2){
Cout & lt; <"./03 _homework_mutiprocess_copy filename "& lt; return -1; 
} 

//the first open source file and get the file size, the size of the distribution of each process according to the three process copy 
Int fd_sor=open (argv [1], O_RDONLY); 
Off_t filesize=lseek (fd_sor, 0, SEEK_END); 
Lseek (fd_sor, 0, SEEK_SET); 
Int wrsize=filesize/3;//wrsize is the size of the process of the first three copy 
Int tlsize=filesize % wrsize;//tlsize is the size of the fourth tail process copy 


//open the target file and expand in line with the source file size 
Char tar_buf [64]={0}; 
Sprintf (tar_buf, copy_ "% s", argv [1]). 
Int fd_tar=open (tar_buf, O_RDWR | O_CREAT | O_TRUNC, 0666); 
//modify the file size is consistent with the copy files 
Ftruncate (fd_tar filesize); 

//the main process to create two file mapping 
Char * sor_p=(char *) mmap (NULL, filesize, PROT_READ MAP_SHARED, fd_sor, 0). 
If (sor_p==MAP_FAILED) 
{
Cout & lt; <"Sor mmap err!" The return - 2; 
} 
Close (fd_sor); 

Char * tar_p=(char *) mmap (NULL, filesize, PROT_READ | PROT_WRITE, MAP_SHARED, fd_tar, 0). 
If (tar_p==MAP_FAILED) 
{
Cout & lt; <"Tar mmap err!" The return - 3; 
} 
Close (fd_tar); 

Char * temp_tar=tar_p; 
Char * temp_sor=sor_p; 

Int id; 

For (id=0; Id & lt; 4. Id + +) 
{
pid_t pid=fork(); 
If (pid==0) 
break; 
} 

If (id & lt; 3) 
{
//the child 0 1 2 
Cout & lt; <"I 'm the child, copying my id=" & lt; //each child process mapping memory copy of 
Memcpy (temp_tar + id * wrsize, temp_sor + id * wrsize, wrsize); 
} 
Else if (id==3) 
{
//the child 3 
Cout & lt; <"I 'm the child, copying my id=" & lt; //map at the end of the last child process for memory copy of 
Memcpy (temp_tar + id * wrsize, temp_sor + id * wrsize, tlsize); 
} 
Else if (id==4) 
{
//parent 
int status; 
Int ret. 
//parent to recycle the child and close the file 

While ((ret=waitpid (- getpid (), & amp; The status, 0))!=1) 
{
If (WIFEXITED (status)) 
{
Cout & lt; <"Recover child success! "& lt; } 
} 

//recovered after the child, the parent disconnect map 
Ret=munmap (sor_p filesize); 
If (ret & lt; 0) 
{
Cout & lt; <"Munmap err!" The return - 4; 
} 

Ret=munmap (tar_p filesize); 
If (ret & lt; 0) 
{
Cout & lt; <"Munmap err!" Return to 5; 
} 

} 





return 0; 
} 

copy the file to open, most can run, but the icon is not correct, I tried others write online program, the somebody else's copy is no problem, where I feel I must have a little problem, but found no problem, I even tried system Ctrl c, Ctrl v, take an examination of to another directory is normal, this let me more confused