#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <unistd.h>
#include <errno.h>
#include <stdio.h>

#define MY_BUFFER_SIZE 1000

ssize_t myRead(int fd,char * buf,size_t count)
{
 ssize_t nb;

 do
 {
  nb=read(fd,buf,count);
 } while((nb==-1)&&
         ((errno==EINTR)||
         (errno==EAGAIN)));
 return(nb);
}

ssize_t myWrite(int fd,const char * buf,size_t count)
{
 ssize_t nb;
 size_t remaining=count;
 const char * ptr=buf;

 do
 {
  nb=write(fd,ptr,remaining);
  if(nb>0) { remaining-=nb; ptr+=nb; }
 } while(remaining&&(nb==-1)&&
         ((errno==EINTR)||
         (errno==EAGAIN)));

 return(nb==-1 ? -1 : (ssize_t)(count-remaining));
}

int main(int argc,char ** argv)
{
 int input, output, stop;
 char buffer[MY_BUFFER_SIZE];
 if(argc<=2)
 {
  fprintf(stderr,"usage: %s input output\n",argv[0]);
  return(1);
 }

 input=open(argv[1],O_RDONLY);
 if(input==-1)
 {
  fprintf(stderr,"Can't open input file %s\n",argv[1]);
  return(1);
 }
 output=open(argv[2],O_WRONLY|O_CREAT|O_TRUNC,0644);
 if(output==-1)
 {
  close(input);
  fprintf(stderr,"Can't open output file %s\n",argv[2]);
  return(1);
 }

 stop=0;
 do
 {
  ssize_t nbR=myRead(input,buffer,MY_BUFFER_SIZE);
  switch(nbR)
  {
    case -1:
      fprintf(stderr,"Error while reading\n");
      stop=1;
      break;
    case 0: /* end of file */
      stop=1;
      break;
    default:
     {
      ssize_t nbW=myWrite(output,buffer,nbR);
      if(nbW==-1)
      {
       fprintf(stderr,"Error while writing\n");
       stop=1;
      }
     }
  }
 } while(!stop);

 close(input);
 close(output);
 return(0);
}