1	/* fileCopy1.c
   2	   This example shows how to do file copy, one block at a time.
   3	   System calls used in this program:
   4	    . write(), read(), open(), close(), exit(), lseek().
   5	*/
     
   6	#include <stdio.h>
   7	#include <fcntl.h>
   8	#include <string.h> 
   9	#include <stdlib.h> 
  10	#include <unistd.h> 
  11	#include <sys/stat.h> 
     
  12	#define FMODE  (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
     
  13	main()
  14	{
  15	   char buf[BUFSIZ];
  16	   char PROMPT1[] = "Please enter source filename >> "; 
  17	   char PROMPT2[] = "Please enter target filename >> "; 
  18	   char ERR1[] = "Can't open source file\n";
  19	   char ERR2[] = "Can't open target file\n";
  20	   char ERR3[] = "Can't read source file\n";
  21	   int fd1, fd2, i, nblock;
  22	   ssize_t nread;
  23	   off_t flen;
     
  24	   write(STDOUT_FILENO, PROMPT1, strlen(PROMPT1)); /* ask for input file */
  25	   nread = read(STDIN_FILENO, buf, BUFSIZ);        /* read from stdin */
  26	   buf[nread-1] = '\0';                   /* strip \n & NULL-terminate buf */
  27	   if ((fd1 = open(buf, O_RDONLY)) == -1) {         /* open for read */
  28	       write(STDERR_FILENO, ERR1, strlen(ERR1));    /* write to stderr */
  29	       return(1);
  30	   }
     
  31	   write(STDOUT_FILENO, PROMPT2, strlen(PROMPT2)); /* ask for output file */
  32	   nread = read(STDIN_FILENO, buf, BUFSIZ);        /* read from stdin */
  33	   buf[nread-1] = '\0';                   /* strip \n & NULL-terminate str */
  34	   if ((fd2 = open(buf, O_WRONLY | O_CREAT | O_TRUNC, FMODE)) == -1) {
  35	       write(STDERR_FILENO, ERR2, strlen(ERR2));    /* write to stderr */
  36	       return(2);
  37	   }
     
  38	   flen = lseek(fd1, 0, SEEK_END);                 /* get file length in char */
  39	   nblock = flen / BUFSIZ;                         /* # of blocks needed */
  40	   
  41	   lseek(fd1, 0, SEEK_SET);                        /* rewind */
  42	   for (i = 0; i <= nblock; i++) {
  43	       nread = read(fd1, buf, BUFSIZ); 
  44	       write(fd2, buf, nread);                     /* save to file 2 */
  45	   }
  46	   if (nread < 0) {
  47	       write(STDERR_FILENO, ERR3, strlen(ERR3));   /* write to stderr */
  48	       return(3);
  49	   }
  50	   close(fd1);                            
  51	   close(fd2);
  52	   exit(0); 
  53	}