Question

C Programming

file.c takes in one input argument that denotes a file to be read. It needs to convert the contents of that file into a character array (char *) and then into a an unsigned character array (unsigned char *).

Please fix and or complete the program, and explain any of the changes too:

----

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

int main(int argc, char *argv[])
{
FILE *f; f = fopen(argv[1], "r");
if( !f ) { exit(1); }
char *tok;
char buf[256];
char *save; // saved data
while(fgets(buf, sizeof(buf), f)
{
tok = strtok(buf, "\0");
save = strcat(save, tok);
}
printf("%s", save); // prints contents
// convert save into an unsigned character array (unsigned char *)
}

----

example.txt // sample text to convert, varies in size/length, can have multiple lines

Hello world.
Have a nice day!

----

run the program (in UNIX) as an executable:
file example.txt // takes in one argument only

Answer 1

Please look at my code and in case of indentation issues check the screenshots.

------------main.c-----------------

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

int main(int argc, char *argv[])
{
   if (argc != 2){               //checks if there are 2 command line arguments ./a.out and filename
       printf("Please provide filename as command line argument\n");
       exit(1);
   }

   FILE * f;
   f = fopen(argv[1], "r");  
   if (!f)                       //report if file cannot be opened
   {
       printf("The input file cannot be opened\n");
       exit(1);
   }

   char buf[256];               //buffer to read a line of data from file      
   char *save = malloc(sizeof(char) * 1024);   //allocate space for storing 1024 characters in the array

   while (fgets(buf, sizeof(buf), f))           //read a line into buf
   {
       save = strcat(save, buf);               //append the line into the char array save
   }
   save[strlen(save)] = '\0';                   //set last character as null character
   printf("%s\n", save);   // prints contents

   unsigned char *save2 = malloc(sizeof(unsigned char) * 1024); //allocate space for storing 1024 unsigned characters in the array
   int i;
   for(i = 0; i < strlen(save); i++)       //loop for each index of save array
   {
       save2[i] = save[i];                       //copy the contents from char array save to unsigned char array save2
   }
   save2[i] = '\0';                           //set last character as null character
   printf("\n%s\n", save2);   // prints contents

}

--------------Screenshots-------------------

----------------------Input--------------------------------------

----------------------Output------------------------------------

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