Getting a directory name from a filename

Question

I have a filename (C:\folder\foo.txt) and I need to retrieve the folder name (C:\folder) in C++. In C# I would do something like this:

string folder = new FileInfo("C:\folder\foo.txt").DirectoryName;

Is there a function that can be used in C++ to extract the path from the filename?

Mahican

Answer 1

There is a standard Windows function for this, PathRemoveFileSpec. If you only support Windows 8 and later, it is highly recommended to use PathCchRemoveFileSpec instead. Among other improvements, it is no longer limited to MAX_PATH (260) characters.

Outdate

Note that this function is now deprecated. The suggestion from Microsoft is to use PathCchRemoveFileSpec instead. – Totalitarian

@Default: PathCchRemoveFileSpec is only available starting with Windows 8. Since Windows Vista and 7 are still supported, so is PathRemoveFileSpec. – Abdulabdulla

Answer 2

Using Boost.Filesystem:

boost::filesystem::path p("C:\\folder\\foo.txt");
boost::filesystem::path dir = p.parent_path();

Embattle

p.remove_filename() will modify p in-place, and may be implemented more efficiently than p = p.parent_path() – Abattoir

If you might also deal with directories be aware of the fact that parent_path() from "C:\\folder" will result in "C:". – Waistline

lots of boost gets upgraded to std so also try this .... include <filesystem> .... std::experimental::filesystem::path p("C:\\folder\\foo.txt"); – Thirtythree

Answer 3

Example from http://www.cplusplus.com/reference/string/string/find_last_of/

// string::find_last_of
#include <iostream>
#include <string>
using namespace std;

void SplitFilename (const string& str)
{
  size_t found;
  cout << "Splitting: " << str << endl;
  found=str.find_last_of("/\\");
  cout << " folder: " << str.substr(0,found) << endl;
  cout << " file: " << str.substr(found+1) << endl;
}

int main ()
{
  string str1 ("/usr/bin/man");
  string str2 ("c:\\windows\\winhelp.exe");

  SplitFilename (str1);
  SplitFilename (str2);

  return 0;
}

Stumper

This is the best minimal solution here. – Asylum

Answer 4

In C++17 there exists a class std::filesystem::path using the method parent_path.

#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
    for(fs::path p : {"/var/tmp/example.txt", "/", "/var/tmp/."})
        std::cout << "The parent path of " << p
                  << " is " << p.parent_path() << '\n';
}

Possible output:

The parent path of "/var/tmp/example.txt" is "/var/tmp"
The parent path of "/" is ""
The parent path of "/var/tmp/." is "/var/tmp"

Heterophyte

There also exists a .remove_filename() method. – Selfsufficient

Thanks, @Qqwy, it also allows to use directory path with that method to get correct and expected results unlike the approach from the answer – Orts

Just be aware that std::filesystem::path may use std::wstring instead of std::string on some platforms, making it difficult to interoperate with normal strings... – Pappy

Answer 5

Why does it have to be so complicated?

#include <windows.h>

int main(int argc, char** argv)         // argv[0] = C:\dev\test.exe
{
    char *p = strrchr(argv[0], '\\');
    if(p) p[0] = 0;

    printf(argv[0]);                    // argv[0] = C:\dev
}

Terra

This is not portable. Path separator in linux is '/'. std::filesystem::path is standard and portable. – Oralee

Its not robust, but can be made portable. Portability is not always required. I prefer this than ask someone to upgrade to C++17 or install Boost. – Cleptomania

Answer 6

 auto p = boost::filesystem::path("test/folder/file.txt");
 std::cout << p.parent_path() << '\n';             // test/folder
 std::cout << p.parent_path().filename() << '\n';  // folder
 std::cout << p.filename() << '\n';                // file.txt

You may need p.parent_path().filename() to get name of parent folder.

Blent

Answer 7

Use boost::filesystem. It will be incorporated into the next standard anyway so you may as well get used to it.

Hyperplasia

Which standard are you talking about? I know that a lot of things from boost were added to C++ std lib, filesystem will be added too? – Sciurine

"It will be incorporated into the next standard anyway" And it's not – Bealle

@AntonK maybe C++ 2017? – Heterophyte

@AlessandroJacopson Cool, it seems included in C++17 - en.cppreference.com/w/cpp/filesystem – Bealle

Answer 8

I'm so surprised no one has mentioned the standard way in Posix

Please use basename / dirname constructs.

man basename

Chapiter

The POSIX functions are not without their drawbacks. In particular they may modify the buffer that you pass in, (they really do mean the signature is basname(char * path) and not basename(const char * path)), and implementations that don't do that appear to have to use a static buffer which makes them thread-unsafe (in principle you could also return dynamically allocated results, but that makes you dependent on alloc family functions which is awkward in C++). – Eastereasterday

Answer 9

_splitpath is a nice CRT solution.

Breban

Answer 10

Standard C++ won't do much for you in this regard, since path names are platform-specific. You can manually parse the string (as in glowcoder's answer), use operating system facilities (e.g. http://msdn.microsoft.com/en-us/library/aa364232(v=VS.85).aspx ), or probably the best approach, you can use a third-party filesystem library like boost::filesystem.

Recap

The standard's C++1z is currently attempting to adopt the boost filesystem library as of now making platform-friendliness much less of an issue. It's still in the experimental headers for MSVC, at least. – Alaster

Answer 11

Just use this: ExtractFilePath(your_path_file_name)

Mikkimiko

I believe this is a Delphi method, not something in C++. – Calcariferous