A primitive folder listing implementation on Windows

Question

I am a recent graduate in computer programming and failed so far to get an internship or a job in the business so I am trying my best to learn from online source. I am trying to implement a dir-like command on Windows, going through a folder and list all files and folder.

What I've learned is to avoid using namespace std; and making the includes in alphabetical orders.

In this code, I am obviously mixing c and c++, good or bad? I am also using Digital Mars as a compiler, I'm trying to avoid installing heavy IDEs and compilers like VS.

All thoughts and critiques are welcome.

#include <iostream>
#include <io.h>
#include <string>
#include <sys/stat.h>
#include <sys/types.h>
#include <windows.h>

bool DirectoryExists( const char* absolutePath ){

if( _access( absolutePath, 0 ) == 0 ){

    struct stat status;
    stat( absolutePath, &status );

    return (status.st_mode & S_IFDIR) != 0;
}
return false;
}

char* replace(const char *s){

char* p = new char[strlen(s)+1];
int i=0;

for (i=0;s[i];i++)  
if (s[i]=='\\') 
    p[i] ='/';
else
    p[i]=s[i];

if (p[i-1] == '/')
    p[i]='\0';
else
{   
    p[i]='/';
    p[i+1]='\0';
}

return p;
}

void dirc (const char* destpath){

HANDLE hFind;
WIN32_FIND_DATA FindFileData;
char filename[256];
size_t i=1;

 if((hFind = FindFirstFile(destpath, &FindFileData)) != INVALID_HANDLE_VALUE)
 {
  do    {
        sprintf (filename, "echo %d-%s", i, FindFileData.cFileName);
        system (filename);
        i++;
        }
while(FindNextFile(hFind, &FindFileData));

FindClose(hFind);
}
}

int main(int argc, char**argv) {

const char* path = argv[1];
char* fspath;

if (argv[1] == NULL)
    {
    std::cout <<"No path provided"<<std::endl;
    return 0;
    }

else
    if ( DirectoryExists(path) )
        std::cout <<"Provided path is "<<path<<std::endl;
    else
        {
        std::cout <<"Path doesn't exist"<<std::endl;
        return 0;
        }
 fspath = replace(path);
 char* destpath = (char *) malloc (strlen(fspath)+6);
 destpath = strcat (fspath,"*.*");
 dirc (destpath);
 free (destpath);

return 0;
}

Answer 1

Thous shalt not mix C/C++ unless you have a good reason to do so. Jokes aside, using pure C++ will lead more bug-free code (in terms of memory management etc.) especially since your statement

What I've learned is to avoid using namespace std; and making the includes in alphabetical orders.

implies (to me) you are a newcomer. You're welcome, by the way. That being said, learning C way of doing things is really helpful, especially if you are not familiar with pointers etc. You will experience first hand, say why C++ smart pointers and containers are a thing.

My advice would be to study exactly why

You should not mix C/C++ unless you have a good reason to do so.

What you are doing with this code is nothing but plain C (except iostream methods). I did not check your code thoroughly though. So why do you want to use C++? If you want to use C++, why do you write C code and compile as C++ (again, except iostream, which can be as well stdio.h)?

Since you are using Digital Mars, for which I can't find any standard compliance information, I am not sure if you can use C++17 STL. If you can, there is a filesystem library which can be used to do what you are trying to accomplish with a few lines of code. If you can't, you can try to find a more up-to-date compiler.

Answer 2

Welcome to the C++ community. You will find a lot of people with outspoken opinions about C++, variating from finding compatibility with C very important to those who find it very dangerous (even in a single person). My opinion: Avoid C unless you have a valid reason to do so, in which case, provide a C API and write the other code in pure C.

Before diving into the code, a small remark: C++17 has std::file_system with a better API than the Windows API.

So to the code:

• const char * is something to avoid, std::string_view and std::string are much better alternatives.
• Don't write struct stat status;, stat status; is sufficient and will confuse less c++ programmers
• Don't declare variables at the top of the function (main), just declare them where you need them
• Use nullptr instead of NULL
• Don't mix malloc and new, use the latter in C++

(PS: For the details, please search online, they can motivate it much better than myself)

If I would be doing your review for a C++ job, I don't like this kind of code to show up. HOWEVER even with that, you could still be hired, cause those things can be taught. What's more important is that you can show how to think about a problem and that you understand C++ concepts.

My next question to you let you show off your knowledge about how to write classes. Public, protected, private, and when to use it. Member functions and variables. How the this-pointer works. What RAII is ...