just read the text contents of a binary file and display it to stdout

[munitjsr2]

#include <stdio.h>
    #include <stdlib.h>
    
    typedef struct filedata
    {
            char data[100];
    }data_t;
    
    data_t * fname=NULL;
    
    //IS AN ARRAY OF the structure filedata REQUIRED HERE
    
    void quit()
    {
          printf("\nPress enter to exit");
          fflush(stdin);
              getchar(); 
    }    
                                         
                    
    int main()
    {
    char ch;   
        fname=(data_t *)malloc(sizeof(data_t));
    
        FILE *fptr=NULL;
        atexit(quit);
        printf("Please enter the file name to read : ");
        fflush(stdin);
        scanf("%s",fname->data);    
        fptr=fopen(fname->data,"rb");
    
        if(fptr == NULL)
        {
                perror("Could not open the file ");
                return;
        }
        printf("\n+++++++++++++++++++++++++++++++++++++++++++++++++++++++++\n");
        printf("Contents of the file %s are : ",fname->data);
    
       <strong> while(fread(&fname, sizeof(data_t), 1,fptr) == 1)
        {
          // what do I put here? 
        }</strong>
    
        fclose(fptr);       
        return 0;
    }

I want to read any binary file contaning some text or numbers in it on my computer and display it on the stdout.

How do I do it?

Shall I declare an array of the structure file data like `data_t data[100]`?
What should I put in the while loop above to display the contents?An example : of course if I know the attributes inside the some stucture like name,age etc then I can do something like

while ( fread ( &e, sizeof ( e ), 1, fp ) == 1 )
printf ( "\n%s %d %f", e.name, e.age, e.bs ) ;

But how do I read any text contents of any binary file and display it to stdout?

Can somebody look into it please... may be I could get an idea or something?

[venomxxl]

You don't have to loop through every byte read.
You can do

fread(&(fname->data), sizeof(char), text_length, fptr);

if you know the amount of characters in the file.
Otherwise you can do

int i = 0;
while(!feof(fptr))
{
fread((&(fname->data)) + i, sizeof(char), 1, fptr);
i++;
}

Remember that you must append a null character to the string.
(you can memset the array before using it so it contains only nulls)

Hope this helps.

PS. I edited out a lot of errors haha :)

[gerard4143]

Really, why would you want to? You know that some of the binary characters have no ascii representation, hence can't be displayed. It would be better to display each binary value in hex, thus displaying each and everyone of them.

[Narue]

Alternatively, use isprint to determine if there's a printable representation of the character, and show the numeric value if there is not.

[munitjsr2]

I got this guys from another forum and the answer from a person named jim was below :

In order to read a binary file you must know how the file was written. You must know how the variables were written, their size, in bytes. Their type, double, float, int, char, user defined type, etc. The order these variables were written to the file. And last the number of bytes required to hold each variable.

So it is usually not possible to take "any" binary file and read the contents. You may read a select binary file that you know the exact layout, but not a binary file that you do not know the layout.

Jim

So thats true hmmm.. its not possible

[gerard4143]

Try compiling this program

testp.c

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

int main(int argc, char**argv)
{
  char ch;
  FILE *fd = NULL;
  
  if ( argc != 2 )
  {
	fputs("usage error - a.out <Filename>\n", stderr);
	exit(EXIT_FAILURE);
  }
  
  if (!(fd = fopen(argv[1], "r")))
  {
	fprintf(stdout, "Could not open %s\n", argv[1]);
	exit(EXIT_FAILURE);
  }
  
  while (fread(&ch, sizeof(char), 1, fd))
  {
	fprintf(stdout, "%p ", (void*)ch);
  }
  
  fclose(fd);
  return 0;
}

Now pass a file name as a command line argument..It should display the binary(hex values) contents of the file.

[munitjsr2]

Gerard , compilation gives error :

testp.c: In function `main':
testp.c:23: warning: cast to pointer from integer of different size

[venomxxl]

It's a warning and it's quite irrelevant. Every pointer is just a number. The compiler warns you that you might make a mistake (e.g. write 32-bit integers into an array of bytes and make a "buffer overflow").

[Narue]

It's a warning and it's quite irrelevant.

It's a warning, but hardly irrelevant. The warning tells me that either the author made a mistake and meant &ch, or was hoping %p would print a hexadecimal value and was trying to be clever. Either way, the code is wrong. The fix for the latter is to recognize that fprintf already supports hexadecimal output without subverting the type system:

fprintf(stdout, "%3x", ch);