trjhtr

I am an aspiring C++ programmer and I have been programming for a few years off and on but I don't have much usable knowledge. Right now I am working on filesystem safety so I decided to write an erasure (think BleachBit).

It needs to be run from terminal as such (root/ program filename.something) and needs to open the file in memory, get file size, write in raw binary format to each bit of file, close file,. This is a part where I am stuck. It needs to delete the (I am pretty sure it's some kind of pointer) object that represents
the file that the system stores by wiping it from memory.

ren.cpp:

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






void bitwrite(int pass, char * fn)

 FILE * fp;
 fp = fopen(fn, "wb");
 int k;
 const void * kptr;
 switch(pass)
 
 case 0:
 k = 0b11111111111111111111111111111111;
 break;
 case 1:
 k = 0b10101010101010101010101010101010;
 break;
 case 2:
 k = 0b01010101010101010101010101010101;
 break;
 case 3:
 k = 0b11111111111111111111111111111111;
 break;
 case 4:
 k = 0b10101010101010101010101010101010;
 break;
 case 5:
 k = 0b01010101010101010101010101010101;
 break;
 case 6:
 k = 0b00000000000000000000000000000000;
 break;
 
 fseek(fp, 0, SEEK_END);
 off_t size = ftell(fp);
 fseek(fp, 0, SEEK_SET);
 for(int a = 0; a<sizeof(size);a++)
 
 fseek(fp, a, SEEK_SET);
 fwrite(&k, sizeof(int), 1, fp);

 
 fclose(fp);


int main(int argc, char * argv)


 if(argv == NULL)
 
 printf("usage: ren file to be destroyed");
 return 1;
 
 for(int i=0;i<7;i++)
 
 bitwrite(i, argv[1]);

 
 printf("success!");

 return 0;

This code needs to run efficiently as possible. I am at a loss as how to improve and fix errors. Currently, C++ ren.cpp -o ren runs without error, but gdb throws a sigseg error @fseek.

Instead of switch, just use an array.

k= pattern[pass];

Don’t use the C macro NULL for any purpose. Banish it from your memory!

The style in C++ is to put the * or & with the type, not the identifier. This is called out specifically near the beginning of Stroustrup’s first book, and is an intentional difference from C style.

Why are you including <string> when you do not use any? There is nothing at all from the C++ standard library here. I would think it was a C program.