Delete file with string variable

[Wedde]

I am trying to delete a .txt file. When hardcoding the .txt, like Banana.txt it functions like expected with the remove function. But when i am trying to use a string variable to choose which file i should remove it says it cant recognise remove.

  void eraseUser() {
    std::string username;
    std::cout << "Which file do you want to erase? (Case sensitive)" << std::endl;
    std::cin >> username;
    std::remove(username + ".txt");
  } 

[jonnin]

try: username+= ".txt" as a new statement and then pass in only username, not the addition.

[Nico]

Have a look at https://en.cppreference.com/w/cpp/io/c/remove

std::remove takes a const char*, not an std::string.

Your compiler should inform you about this with something like:

error: cannot convert 'std::__cxx11::basic_string<char>' to 'const char*' for argument '1' to 'int remove(const char*)'

Consider:

    std::cin >> username;
    username = username + ".txt";
    std::remove(username.c_str());

Kind regards, Nico

[Wedde]

std::remove(username.c_str());

How do i understand the .c_str() ??

[deleted account xyzzy]

c_str() returns a non-modifiable standard C character array version of the string.
https://en.cppreference.com/w/cpp/string/basic_string/c_str

[jonnin]

.c_str() returns a C style string, which is just an array of characters, which is how the C language (and C++ inherits this capacity) handles 'strings'.

[Wedde]

Ok so because the remove function cant handle strings we need to convert our strings to chars to use it?

[jonnin]

yes, looks like.

do you have <filesystem>?
https://en.cppreference.com/w/cpp/filesystem/remove
that is built from an unnecessary path-object that is built from C++ string objects.

[seeplus]

@nico. That link doesn't work as it treats the final . as part of the link! You need to have at least one white-space before/after . Try https://en.cppreference.com/w/cpp/io/c/remove

delete is part of the C library - so doesn't know anything about std::string.

[JLBorges]

std::filesystem::remove is part of the C++ library. https://en.cppreference.com/w/cpp/filesystem/remove

It accepts std::filesystem::path and therefore we can pass std::string or std::string_view
(or for that matter any sequence of characters) to it.
https://en.cppreference.com/w/cpp/filesystem/path/path

[Wedde]

So it would be better to use the <filesystem> header and use remove from there? Because we are working in c++. And then i would not need to make the string to a char array?

[deleted account xyzzy]

When writing new C++ code using newer standard C++ constructs and libraries is a good idea.

Although also knowing the C library as well as older C++ standards is also a good thing because it makes understanding and maintaining older code that works less of a headache.

Updating older code to a newer standard is a great learning/intellectual exercise, just don't do it on production code unless the company wants it.

[Wedde]

I have looked at <filesystem> remove / remove all and I am not sure how its should be implemented.

    void eraseUserC() {
    std::string username;
    std::cout << "Which file do you want to erase? (Case sensitive)" << std::endl;
    std::cin >> username;
    
      if(bool remove(const username + ".txt")){
        std::cout << "File succesfully removed." << std::endl;
      }
      else std::cout << "Error, file could not be found or removed" << std::endl;
    }

This gives me error "A function type is not allowed here" I am trying to use the documentation.

[jonnin]

bool does not belong on line 6, nor does const.
those are part of how it is defined, but not seen when you *use* it.

[Wedde]

I would appreciate a short code example.

If i understand correctly remove is a function, so why do i need to define it?

[deleted account xyzzy]

Your latest code snippet defines a standalone function named remove. You simply USE std::filesystem::remove.

#include <iostream>
#include <fstream>
#include <filesystem>
#include <string>

int main()
{
   std::string fname{ "dummy" };

   // let's create a file and put some data in it
   std::ofstream ofile(fname + ".txt");
   ofile << "Some text";
   ofile.close();

   // let's read the file and display the contents
   std::ifstream ifile(fname + ".txt");
   std::string str;
   std::getline(ifile, str);
   ifile.close();

   std::cout << str << "\n\n";

   // let's try to remove the file created earlier
   if (std::filesystem::remove(fname + ".txt"))
   {
      std::cout << "File removed....\n";
   }
   else
   {
      std::cout << "File doesn't exist!\n";
   }
}

Some text

File removed....

[Wedde]

Thank you. It worked but the compiler gave me a error and a fix. In the end the code looked like.

void eraseUserC() {
    std::string username;
    std::cout << "Which file do you want to erase? (Case sensitive)" << std::endl;
    std::cin >> username;
    if(std::__fs::filesystem::remove(username + ".txt")){
        std::cout << "File succesfully removed." << std::endl;
    }
    else std::cout << "Error, file could not be found or removed" << std::endl;
    
}

what does the fs do?

[deleted account xyzzy]

You are combining code snippets into a royal mess. That fs crap is from namespace fs = std::filesystem;, a way of reducing key-strokes. Did you notice I don't use it?

Just fully qualify the std::filesystem::remove function, as I did.

OR use the namespace qualifier and call the function as if (fs::filesystem::remove(username + ".txt"))

If that use of namespace confuses you DON'T USE IT.

It doesn't confuse me, though I still won't use it.

Trying to save a couple of keystrokes by all these namespace short-cuts can be a huge source of errors as you've discovered. I learnt this lesson the HARD WAY.

[Devendra238]

I performed these operations but different way, the following method I'm using..

#include<iostream>
#include<fstream>
#include<stdio.h>  // rename, remove
using namespace std;

int main() 
 {
   char name[20],filename[20],newname[20];

/*create filename*/
    cout<<"Enter file-name to create: ";
    gets(filename);
    ofstream fout(filename);

/*save record into file*/
    cout<<"\nEnter a name to store in it: ";
    gets(name);
    fout<<name;
    fout.close();
    cout<<"\nrecord saved into file called - "<<filename<<endl;

/*rename file*/
    cout<<"\nHit to Rename this file";
  
    cout<<"\nEnter new name: ";
    gets(newname);
    rename(filename,newname);
    cout<<"\nNow file name is: "<<newname<<endl;
/*remove file*/   
    cout<<"\nHit to remove file\n";

    remove(newname);
    cout<<"\nfile removed successfully...";
   
 }

OUTPUT

Enter file-name to create: database

Enter a name to store in it: rahul

record saved into file called - database

HIT ENTER to Rename this file
Enter new name: file

Now file name is: file

HIT ENTER to Remove file

file removed successfully...