linux--multiple processes for file copies

When learning Io, we have used the file IO function, the standard IO function has implemented a copy of the file,

When copying a file, we can consider several ways:

A. Single Process copy:

Assuming that a file requires a copy of 100 bytes, each time slice can be copied 20 bytes of work, you need to be allocated 5 time slices to complete the task, but the problem is that these time slices are not continuously allocated, we do not know

We have a second way to solve this problem by how much time it takes for the next time slice to be allocated to the process.

B. Multi-process copy (single core single CPU):

By switching processes, as the number of processes increases, it takes less time for the current program to get time slices.

C. Multi-process copy (multi-core concurrency processing)

We are going to implement the second method, the code is as follows:

1#include <stdio.h>2#include <stdlib.h>3#include <unistd.h>4#include <fcntl.h>5#include <string.h>6#include <sys/types.h>7#include <sys/stat.h>8#include <sys/wait.h>9 intCutting (Char*SRC,intProno)Ten { One     intfd,filesize; A     if((Fd=open (src,o_rdonly)) ==-1) -     { -Perror ("Cutting Open failed"); the     return-1; -     } -     if(Filesize=lseek (FD,0, seek_end)) ==-1) -     { +Perror ("FileSize failed"); - Close (FD); +         return-1; A     } at     intblocksize; -     if(filesize%prono==0) -     { -blocksize=filesize/Prono; -     } -     Else in     { -blocksize=filesize/prono+1; to     } + Close (FD); -     //printf ("%d", blocksize); the     returnblocksize; *  $ }Panax Notoginseng intCopyChar*SRC,Char*des,intPosintblocksize) - { the     if(Access (SRC,F_OK) ==-1) +     { APerror ("Acess failed"); the     } +     intfd1,fd2; -     CharBuf[blocksize]; $fd1=open (src,o_rdonly); $Fd2=open (des,o_wronly| O_creat,0664); - Lseek (fd1,pos,seek_set); - Lseek (fd2,pos,seek_set); the  - Wuyi     intLen=read (Fd1,buf,sizeof(BUF)); the write (Fd2,buf,len); - Close (FD1); Wu Close (FD2); -     return 1; About } $ intCreateChar*SRC,Char*des,intBlockSizeintProno) - { -     inti; - pid_t pid; A     intpos=0; +      for(i=0; i<prono;i++) the     { -Pid=fork (); $         if(pid>0) the         { thepos+=blocksize; the  the             //printf ("The current read location is:%d, each time the file size is read:%d, the current process is%d\n", pos,blocksize,getpid ()); -             in     } the  the         Else if(pid==0) About         { the copy (src,des,pos,blocksize); the              theprintf"The current read location is:%d, each time the file size is read:%d, the current process is%d\n", Pos,blocksize,getpid ()); +              Break; -         } the         Bayi     } the     return 1; the } - intMainintargcChar**argv) - { the     intProno; the     intblocksize; the     if(argc<3) the     { -printf"The Canshu you have Chuan is too less\n"); the     } the     if(argv[3]!=0) the     {94Prono=atoi (argv[3]); the         if(prono<=0|| prono>= -) the         { theprintf"The num of the process you give cant isn't less than 0 or more than 100\n");98         } About          -     }101     Elseprono=5;102Blocksize=cutting (argv[1],prono);103Create (argv[1],argv[2],blocksize,prono);104  the     return 0;106}

linux--multiple processes for file copies