How do you check if a file exists

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I am trying to see if a file exist before I copy the file to the path. I thought it would be simple but the method I tried got “std::ios_base::fail: non-standard syntax; use ‘&’ to create a pointer to member” was the error I got. I am probably being an idiot but I have only just started learning C++ so I still need to learn a bit.

What I have tried:

C++

Bool FileExists(const char * filename)
{
    Bool data = true;
    ifstream file(filename);
    If(file.fail)
    {
         Return data;
    }
    Else
    {
         Data = true;
         Return data;
    }
}

Sorry if this looks bad is because I am on my phone.

Posted 28-Jan-19 23:59pm

WOLF 2018

Updated 29-Jan-19 4:27am

RickZeeland

v2

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4 solutions

Solution 3

I found a Solution here I hope it works Checking whether a file exists or not[^]

Is a very simple method.

Posted 29-Jan-19 0:58am

WOLF 2018

Comments

Richard MacCutchan 29-Jan-19 7:11am

Did you notice that your code returns true in both cases?

CPallini 29-Jan-19 7:41am

It actually Returns true. :-)

Richard MacCutchan 29-Jan-19 8:53am

:)

[no name] 29-Jan-19 13:54pm

I think it will not compile :-)

Usman Hunjra 29-Jan-19 12:53pm

nice catch Sir .. ;)

Solution 2

Modern C++ makes your life easier: std::filesystem::exists - cppreference.com[^].

Posted 29-Jan-19 0:12am

CPallini

Comments

WOLF 2018 29-Jan-19 6:44am

Unfortunately that didn’t work. My computer can’t find std::filesystem and I have included it.

CPallini 29-Jan-19 7:38am

A C++17 compliant compiler is required.

Solution 1

Assuming you are using Visual Studio, see answer here: How to check if a file exists with stat in visual studio c++ 2010? - Stack Overflow[^]

Posted 29-Jan-19 0:10am

RickZeeland

Comments

WOLF 2018 29-Jan-19 6:46am

Just finished reading this but I don’t understand where I can return true or false. I just want a simple method.

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Rick York · Accepted Answer · 2019-01-29T04:27:00

Solution 4

Here is what I use in windows :

C++

// see if a file is accessible and is not a directory

bool CheckFileAccess( PCTSTR filename )
{
    bool state = true;
    DWORD attrib = GetFileAttributes( filename );
    if( attrib == INVALID_FILE_ATTRIBUTES )
    {
        state = false;      // not accessible
    }
    else if( attrib & FILE_ATTRIBUTE_DIRECTORY )
    {
        state = false;      // it is a directory
    }
    return state;
}

Posted 29-Jan-19 4:27am

Rick York

Comments

Rick York 30-Jan-19 0:52am

Given this, it is a simple extrapolation to arrive at an IsDirectory() type of function.

WOLF 2018 31-Jan-19 16:09pm

Thanks I will give that a try