How can I check if directory is empty ?

Question

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I'm setting up my new code about changing files names, my program is just changes the file names in a specific path, I using filesystem library. My problem is that when there is nothing in the path ( In my case its downloads's path ) if there is nothing there, I'm getting run time error in case that there is no memory.

I want to check if there is a something in a directory and if not just don't do nothing there, just continue, my program is not working if there is nothing in a directory and its annoying.

How can i do this ?

C++

srand(time(0));
string dirPath = "C:\\Users\\" + username() + "\\Downloads\\";
auto path = fs::path(dirPath);
auto dir = fs::recursive_directory_iterator(path);
filesystem::path currPath = path;
auto innerPaths = vector<fs::path>();
innerPaths.push_back(currPath);
int fileName = rand() % 1920;
auto currentDepthSize = dir.depth();

for (auto& block : dir)
{
    if (currentDepthSize != dir.depth())
    {
        currentDepthSize = dir.depth();
        currPath = innerPaths[currentDepthSize];
    }
    if (block.is_directory())
    {
        currentDepthSize = dir.depth();
        currPath = dir->path();
        innerPaths.push_back(currPath);
    }
    else
    {
        string filedata = (currPath.string() + to_string(fileName));
        fs::rename(block.path(), filedata);
        fileName++;
        fstream file_data(filedata);
        file_data << randomString();
        file_data.close();
    }
}

What I have tried:

I already tried to check if directory is empty, but without success.

Posted 1-Nov-19 23:25pm

CodingUniversity

Updated 2-Nov-19 8:14am

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Comments

Richard MacCutchan 2-Nov-19 9:03am

Which line is the check for empty directory in the above code, and what happens when it is executed?

[no name] 2-Nov-19 10:28am

This is the case, i don't know how to check if directory is empty, and if it is, just continue, i tried to use fs::is_empty but with success

Richard MacCutchan 2-Nov-19 11:03am

See my suggested solution below.

3 solutions

Solution 1

You can use PathIsDirectoryEmptyA function (shlwapi.h) | Microsoft Docs[^]

Posted 2-Nov-19 4:24am

Michael Haephrati

Comments

[no name] 2-Nov-19 10:30am

I wan't to use the function in filesystem library, "is_empty".
It's much easier to me to understand, it will be amazing if you will help me with this.

Michael Haephrati 2-Nov-19 10:32am

Found it here: https://docs.w3cub.com/cpp/types/is_empty/

#include <iostream>
#include <type_traits>

struct A {};

struct B {
int m;
};

struct C {
static int m;
};

struct D {
virtual ~D();
};

union E {};

struct F {
[[no_unique_address]] E e;
};

int main()
{
std::cout << std::boolalpha;
std::cout << "A " << std::is_empty::value << '\n';
std::cout << "B " << std::is_empty::value << '\n';
std::cout << "C " << std::is_empty<c>::value << '\n';
std::cout << "D " << std::is_empty<d>::value << '\n';
std::cout << "E " << std::is_empty<e>::value << '\n';
std::cout << "F " << std::is_empty<f>::value << '\n'; // the result is ABI-dependent

}

[no name] 2-Nov-19 10:34am

No, you are using std::is_empty, and im using filesystem library so the function is "fs::is_empty".

And your code is much different than my code, but thank you for your help.

If you can just connect it to my code, it will be so nice from you.

Mohibur Rashid 2-Nov-19 10:41am

https://en.cppreference.com/w/cpp/filesystem/is_empty
does this help?

[no name] 2-Nov-19 10:42am

Like i said, i already tried it but i don't know how to connect it to my code. please help me (:

Solution 2

This (like much of <filesystem>) is not yet a mainstream part of the C++ standard, so you need to use the experimental methods. Something like:

C++

if (experimental::filesystem::v1::is_empty(block.path))
{
    // the directory does not contain any entries
}
else
{
    // not empty so process the entries
}

Posted 2-Nov-19 5:03am

Richard MacCutchan

Comments

[no name] 2-Nov-19 11:04am

Thank you very much! How can i continue the program if there is nothing in the directory?

[no name] 2-Nov-19 11:10am

I tried to do like this, if there is nothing just exit the program, not working for me, still getting run time error in case that there is nothing in this path

();
	innerPaths.push_back(currPath);
	int fileName = rand() % 1920;
	auto currentDepthSize = dir.depth();

	for (auto& block : dir)
	{
		if (fs::is_empty(block.path()))
		{
			exit(0);
		}
		if (currentDepthSize != dir.depth())
		{
			currentDepthSize = dir.depth();
			currPath = innerPaths[currentDepthSize];
		}
		if (block.is_directory())
		{
			currentDepthSize = dir.depth();
			currPath = dir->path();
			innerPaths.push_back(currPath);
		}
		else
		{
			string filedata = (currPath.string() + "\\" + to_string(fileName));
			fs::rename(block.path(), filedata);
			fileName++;
			fstream file_data(filedata);
			file_data << randomString();
		    file_data.close();
		}
	}">

Richard MacCutchan 2-Nov-19 11:28am

Why are you calling exit if you find an empty directory? All you need to do is ignore it and continue the loop.

And please stop just saying "error". Explain exactly what error you are seeing and what line of code it occurs on.

[no name] 2-Nov-19 11:29am

Okay im sorry, how can i ignore it ?

Richard MacCutchan 2-Nov-19 11:30am

Look at the code sample I gave you.

[no name] 2-Nov-19 11:32am

Should i just put break in the if ?

[no name] 2-Nov-19 11:34am

Ok, i tried to add break but im still getting run time error, this error
Exception thrown: read access violation.
_My_data was 0x48.

This is moving me to filesystem program information, not specific in my program line.

[no name] 2-Nov-19 11:38am

Sorry, but your code is not working for me. ):

Richard MacCutchan 2-Nov-19 11:55am

What is not working? All you need to do if the item is a directory is to test if it is empty. If it is not empty then process it as normal.

if (block.is_directory())
{
    if (!fs::is_empty(block.path()))
    {
        currentDepthSize = dir.depth();
        currPath = dir->path();
        innerPaths.push_back(currPath);
    }
}

[no name] 2-Nov-19 11:57am

Thanks, but still not working for me ):

Still getting the this error Exception thrown: read access violation.
_My_data was 0x48. that means that there is no memory in the path.

Richard MacCutchan 2-Nov-19 12:04pm

Please stop saying "not working", it means nothing. Explain exactly what the error is and where it occurs. You have made so many changes to your code it is impossible to guess which line is failing or why.

[no name] 2-Nov-19 12:07pm

The new code that you gave is not working for, let me explain, i'm getting run time error.
this type of error, whice means the is nothing in the directory.
read access violation.
_My_data was 0x48"

And the error is not falling in any line, just stops the program .

Richard MacCutchan 2-Nov-19 12:11pm

I have tested that code in a number of different situations and it works fine. I have no idea what you are doing differently, as not all the relevant code is visible. I suggest you use your debugger to step through the code and find out exactly where the error occurs.

[no name] 2-Nov-19 13:17pm

So why the code is not working for, maybe you can send for me the full code that you working for you ? Maybe im missing something.

Add a Solution

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard MacCutchan · Accepted Answer · 2019-11-02T06:43:00

Solution 3

The following simple code definitely works. Adapt it as necessary to your own requirements.

C++

void SimpleTest()
{
    auto mydocs = fs::path(LR"(C:\Users\ ...)"); // add a valid filesystem path here
    auto dir = fs::recursive_directory_iterator(mydocs);
    fs::path currPath = mydocs;
    
    for (auto& block : dir)
    {
        if (fs::is_directory(block.path()))
        {
            if (fs::is_empty(block.path()))
            {
                cout << block.path() << " is empty" << endl;
            }
            else
            {
                wcout << block.path() << endl;
            }
        }
    }
}

Posted 2-Nov-19 6:43am

Richard MacCutchan

Comments

[no name] 2-Nov-19 12:49pm

Does not working for me, is there anything wrong here ?
if (currentDepthSize != dir.depth())
{
currentDepthSize = dir.depth();
currPath = innerPaths[currentDepthSize];
}
if (block.is_directory())
{
currentDepthSize = dir.depth();
currPath = dir->path();
innerPaths.push_back(currPath);
}
if (fs::is_directory(block.path()))
{
if (fs::is_empty(block.path()))
{
cout << block.path() << " is empty" << endl;
}
else
{
string filedata = (currPath.string() + "\\" + to_string(fileName));
fs::rename(block.path(), filedata);
fileName++;
fstream file_data(filedata);
file_data << randomString();
file_data.close();
}
}

Richard MacCutchan 2-Nov-19 13:22pm

Yes. The block of code starting with if (block.is_directory()). The directory_entry Class does not contain a method named is_directory(), so I do not know why this is being accepted by your compiler.

[no name] 2-Nov-19 13:37pm

Does not working for me, again. ):

srand(time(0));
	string dirPath = "C:\\Users\\" + username() + "\\Downloads";
	auto path = fs::path(dirPath);
	auto dir = fs::recursive_directory_iterator(path);
	filesystem::path currPath = path;
	auto innerPaths = vector<fs::path>();
	innerPaths.push_back(currPath);
	int fileName = rand() % 1920;
	auto currentDepthSize = dir.depth();

	for (auto& block : dir)
	{
		if (currentDepthSize != dir.depth())
		{
			currentDepthSize = dir.depth();
			currPath = innerPaths[currentDepthSize];
		}
		if (fs::is_directory(block.path()))
		{
			if (fs::is_empty(block.path()))
			{
				cout << block.path() << " is empty" << endl;
			}
			else
			{
				string filedata = (currPath.string() + "\\" + to_string(fileName));
				fs::rename(block.path(), filedata);
				fileName++;
				fstream file_data(filedata);
				file_data << randomString();
				file_data.close();
			}
		}
	}

Can you please just post your full code ? Maybe i'm missing something ):
I'm so confused.

Richard MacCutchan 2-Nov-19 13:46pm

I have given you my full code, which is just a sample of how to iterate a directory tree and check if a directory is empty or not. I suggest you start with that basic code and check the output matches what you see with File Explorer. You can then add code to the block where a directory is not empty to do the additional work that your program needs. Do not add all the extra code in one go, build it up one piece at a time so you can check that it still works at each stage. That will also help to identify problems when a new piece of code causes an error, or does not produce the correct output.

[no name] 2-Nov-19 13:56pm

Okay, i tried to find my problem and this is this 2 lines of code, this is gives me the problem

auto innerPaths = vector<fs::path>();
auto currentDepthSize = dir.depth();

How can i fix this ? i need them because for the other if statements.

Richard MacCutchan 2-Nov-19 13:58pm

Sorry, no idea. As I keep repeating, you need to explain exactly what is failing, people here cannot see your screen so have no idea what is going on.

[no name] 2-Nov-19 14:13pm

OMG!!!!!!!!!!!! ITS WORKING FOR ME THANK YOU!!!!!!!!!!!!!!!!!

[no name] 2-Nov-19 14:00pm

I'm not getting any errors, but without this and the other 2 if's statements, the files does not renaming.

How can i use this both of 2 lines of code without getting any runtime error ?

How can I check if directory is empty ?

3 solutions

Solution 1

Solution 2

Solution 3

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How can I check if directory is empty ?

3 solutions

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Solution 3

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