C program to learn posix function. Copy a file.

filecopy.c

#include <stdio.h>
#include <stdlib.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>

#define BUFFER_SIZE 256

void handleError(char* message, char* secondMessage, int checkNum);

int main(int argc, char** argv)
{
  int  readfd,
       writefd,
       rcount,
       wcount,
       totalByte = 0,
       closeRead,
       closeWrite,
       xid;
  char buffer[BUFFER_SIZE];

  // confirm that the correct number of arguments were passed.
  if (argc < 3 || argc > 3 ) {
    printf("filecopy: invalid number of arguments\n");
    printf("usage: filecopy <sourcefile> <destinationfile>\n");
    return 1;
  }

  // Opens a designated file for reading 
  readfd = open(argv[1], O_RDONLY, 0);

  // Error if file didn't open
  handleError("Unable to open", argv[1], readfd);
  

  // Creates a new file named, sets read/write permissions for user 
  // and read permissions for group and other
  writefd = creat(argv[2], S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);

  // Error if file create failed 
  handleError("Unable to create", argv[2], writefd);

  do  {
    // Read up to BUFFER_SIZE bytes from the file into the buffer. 
    rcount = read(readfd, buffer, BUFFER_SIZE);

    // Error if read failed 
    handleError("Unable to read", "data", rcount);

    // No more data found exit loop
    if (rcount == 0) {
      break;
    }

    // Write to a file the contents of buffer, up to rcount number of bytes 
    wcount = write(writefd, buffer, rcount);

    // Error if write failed 
    handleError("Unable to write to", argv[2], wcount);

    // Tally total count for output
    totalByte = totalByte + wcount;
  } while(rcount != 0);


  // Close output file
  closeWrite = close(writefd);

  // Error closing write file 
  handleError("Unable to close", argv[2], closeWrite);
  

  // Close input file
  closeRead = close(readfd);

  // Error closing input file 
  handleError("Unable to close", argv[1], closeRead);

  printf("copied %d bytes from file %s to %s\n", totalByte, argv[1], argv[2]);
   
  return 0;
}

void handleError(char* message, char* secondMessage, int checkNum) {
  if (checkNum == -1) {
    printf("%s %s: %s\n", message, secondMessage, strerror( errno ));
    exit(1);
  }
}