1  /* fileCopy.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().
   5  */
     
   6  #include <stdio.h>
   7  #include <fcntl.h>
   8  #include <unistd.h> 
   9  #include <sys/stat.h> 
     
  10  #define FMODE  (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
     
  11  main()
  12  {
  13     char buf[BUFSIZ];
  14     char PROMPT1[] = "Please enter source filename >> "; 
  15     char PROMPT2[] = "Please enter target filename >> "; 
  16     char ERR1[] = "Can't open source file\n";
  17     char ERR2[] = "Can't open target file\n";
  18     char ERR3[] = "Can't read source file\n";
  19     int fd1, fd2;
  20     ssize_t nread;
     
  21     write(STDOUT_FILENO, PROMPT1, strlen(PROMPT1)); /* ask for input file */
  22     nread = read(STDIN_FILENO, buf, BUFSIZ);        /* read from stdin */
  23     buf[nread-1] = '\0';                   /* strip \n & NULL-terminate buf */
  24     if ((fd1 = open(buf, O_RDONLY)) == -1) {         /* open for read */
  25         write(STDERR_FILENO, ERR1, strlen(ERR1));    /* write to stderr */
  26         return(1);
  27     }
     
  28     write(STDOUT_FILENO, PROMPT2, strlen(PROMPT2)); /* ask for output file */
  29     nread = read(STDIN_FILENO, buf, BUFSIZ);        /* read from stdin */
  30     buf[nread-1] = '\0';                   /* strip \n & NULL-terminate str */
  31     if ((fd2 = open(buf, O_WRONLY | O_CREAT | O_TRUNC, FMODE)) == -1) {
  32         write(STDERR_FILENO, ERR2, strlen(ERR2));    /* write to stderr */
  33         return(2);
  34     }
     
  35     while ((nread = read(fd1, buf, BUFSIZ)) > 0) {    /* while not EOF */
  36         write(fd2, buf, nread);                     /* save to file 2 */
  37     }
  38     if (nread < 0) {
  39         write(STDERR_FILENO, ERR3, strlen(ERR3));   /* write to stderr */
  40         return(3);
  41     }
  42     close(fd1);                            
  43     close(fd2);
  44     exit(0); 
  45  }