Question

GIVEN CODE. PLEASE FILL IN THE BLANK.

Implement a program to display a file's contents. It should be similar to the UNIX cat command when given a single file. Name your command show. It should have the following syntax: $ ./ show fileName The above program displays the contents of the file named fileName. Each system call must have error checking, and print an error message if it occurs. You must use open(), read(), write() and close() system calls. 10 points each.

// Include Block
#include <fcntl.h>
#include <unistd.h>

// Preprocessor declarations
#define BUF_SIZE 10 /* global constant buffer size: Generally this would be much larger, but I want to show you that it works in a loop until the entire file is read.*/

// main function
int main(int argc, char *argv[])
{
   // Variable declarations
   int fd;                       // file descripter
   char buffer[BUF_SIZE];       // string for buffer between read and write
   long n;                       // amount read by read()

   if (____ != 2)
   {
       write(STDOUT_FILENO, "Usage: show filename\n", 21);
       return 1;
   }

   // Open the file given as an argument by the user
   if ((____ = open(____, O_RDONLY)) == -1 )
   {
       // Report error opening
       write(STDERR_FILENO, "Error opening file.\n", 20);
       return 1;
   }

   // Loop through until nothing is read
   while ( (____ = read(____, ____, ____)) > 0 )
   {  
       // Write what was read to the stdout
       if( write(STDOUT_FILENO, ____, ____) != n )
       {
           //report error writing
           write(STDERR_FILENO, "Error writing character.\n", 25);
           return 3;
       }
   }

   // Error check
   if(____ == -1)
   {
       // report error reading
       write(STDERR_FILENO, "Error reading character.\n", 24);
       return 2;
   }

   /* If we got here that means n=0, meaning it successfully read and wrote
   the whole file without error, and there is nothing left to read. */

   // Close the file
   close(____);

   // Success:
   return 0;
}

Answer 1

--> Below is the program with blanks filled appropriately in bold letters

Code:

// Include Block
#include <fcntl.h>
#include <unistd.h>

// Preprocessor declarations
#define BUF_SIZE 10

/* global constant buffer size: Generally this would be much larger,
but I want to show you that it works in a loop until the entire file is read.*/

// main function
int main(int argc, char *argv[])
{
   // Variable declarations
   int fd;                       // file descripter
   char buffer[BUF_SIZE];       // string for buffer between read and write
   long n;                       // amount read by read()

   if (argc != 2)   //checking argument count
   {
       write(STDOUT_FILENO, "Usage: show filename\n", 21);
       return 1;
   }

   // Open the file given as an argument by the user
   if ((fd = open(argv[1], O_RDONLY)) == -1 )
   {
       // Report error opening
       write(STDERR_FILENO, "Error opening file.\n", 20);
       return 1;
   }

   // Loop through until nothing is read
   while ( (n = read(fd, buffer, BUF_SIZE)) > 0 )
   {
       // Write what was read to the stdout
       if( write(STDOUT_FILENO, buffer, n) != n )
       {
           //report error writing
           write(STDERR_FILENO, "Error writing character.\n", 25);
           return 3;
       }
   }

   // Error check
   if(n == -1)
   {
       // report error reading
       write(STDERR_FILENO, "Error reading character.\n", 24);
       return 2;
   }

   /* If we got here that means n=0, meaning it successfully read and wrote
   the whole file without error, and there is nothing left to read. */

   // Close the file
   close(fd);

   // Success:
   return 0;
}