Simple copy program hangs?

This simple file copy program hangs and I don't know why. Help!

Code:

//simple copy file program

#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>

#include <iostream>
using std::cout;

int main(int argc,char **argv)
{
  // validate correct command line arguments
  if (argc!=3){
    cout << "Usage: copy_system <srcpath> <destpath>\n";
    exit(1);
  }

  
  char block[1024];// buffer for file copying
  int in, out;// source and destination file descriptors
  int nread;//bytes read from source

  // open source as read only
  if ((in=open(argv[1],O_RDONLY))==-1){
    cout << "Error opening file:" << argv[1] << "\n";
    exit(1);
  }

  //create destination file with owner read and write permissions set
  out=open(argv[2], O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR);

  // read data into buffer from source and copy to destination
  while ((nread=read(in,block,sizeof(block)))>0)
    write(out,block,nread);

  exit(0);
}

No idea - works on my system.
How did you run it from the command line?

>>out=open(argv[2], O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR);
You didn't error check this one, maybe there's a problem opening/writing to the file.

Run it under a debugger to find out more...

ok thanks I'll check it out and add some error checking.