Get a file name from a path

What is the simplest way to get the file name that from a path?

string filename = "C:\\MyDirectory\\MyFile.bat"

In this example, I should get "MyFile". without extension.

Solution 1:

The task is fairly simple as the base filename is just the part of the string starting at the last delimeter for folders:

std::string base_filename = path.substr(path.find_last_of("/\\") + 1)

If the extension is to be removed as well the only thing to do is find the last . and take a substr to this point

std::string::size_type const p(base_filename.find_last_of('.'));
std::string file_without_extension = base_filename.substr(0, p);

Perhaps there should be a check to cope with files solely consisting of extensions (ie .bashrc...)

If you split this up into seperate functions you're flexible to reuse the single tasks:

template<class T>
T base_name(T const & path, T const & delims = "/\\")
{
  return path.substr(path.find_last_of(delims) + 1);
}
template<class T>
T remove_extension(T const & filename)
{
  typename T::size_type const p(filename.find_last_of('.'));
  return p > 0 && p != T::npos ? filename.substr(0, p) : filename;
}

The code is templated to be able to use it with different std::basic_string instances (i.e. std::string & std::wstring...)

The downside of the templation is the requirement to specify the template parameter if a const char * is passed to the functions.

So you could either:

A) Use only std::string instead of templating the code

std::string base_name(std::string const & path)
{
  return path.substr(path.find_last_of("/\\") + 1);
}

B) Provide wrapping function using std::string (as intermediates which will likely be inlined / optimized away)

inline std::string string_base_name(std::string const & path)
{
  return base_name(path);
}

C) Specify the template parameter when calling with const char *.

std::string base = base_name<std::string>("some/path/file.ext");

Result

std::string filepath = "C:\\MyDirectory\\MyFile.bat";
std::cout << remove_extension(base_name(filepath)) << std::endl;

Prints

MyFile

Solution 2:

A possible solution:

string filename = "C:\\MyDirectory\\MyFile.bat";

// Remove directory if present.
// Do this before extension removal incase directory has a period character.
const size_t last_slash_idx = filename.find_last_of("\\/");
if (std::string::npos != last_slash_idx)
{
    filename.erase(0, last_slash_idx + 1);
}

// Remove extension if present.
const size_t period_idx = filename.rfind('.');
if (std::string::npos != period_idx)
{
    filename.erase(period_idx);
}

Solution 3:

The Simplest way in C++17 is:

use the #include <filesystem> and filename() for filename with extension and stem() without extension.

#include <iostream>
#include <string>
#include <filesystem>
namespace fs = std::filesystem;

int main()
{
  std::string filename = "C:\\MyDirectory\\MyFile.bat";

  std::cout << fs::path(filename).filename() << '\n'
    << fs::path(filename).stem() << '\n'
    << fs::path("/foo/bar.txt").filename() << '\n'
    << fs::path("/foo/bar.txt").stem() << '\n'
    << fs::path("/foo/.bar").filename() << '\n'
    << fs::path("/foo/bar/").filename() << '\n'
    << fs::path("/foo/.").filename() << '\n'
    << fs::path("/foo/..").filename() << '\n'
    << fs::path(".").filename() << '\n'
    << fs::path("..").filename() << '\n'
    << fs::path("/").filename() << '\n';
}

Which can be compiled with g++ -std=c++17 main.cpp -lstdc++fs, and outputs:

"MyFile.bat"
"MyFile"
"bar.txt"
"bar"
".bar"
""
"."
".."
"."
".."
"/"

Reference: cppreference

Solution 4:

The simplest solution is to use something like boost::filesystem. If for some reason this isn't an option...

Doing this correctly will require some system dependent code: under Windows, either '\\' or '/' can be a path separator; under Unix, only '/' works, and under other systems, who knows. The obvious solution would be something like:

std::string
basename( std::string const& pathname )
{
    return std::string( 
        std::find_if( pathname.rbegin(), pathname.rend(),
                      MatchPathSeparator() ).base(),
        pathname.end() );
}

, with MatchPathSeparator being defined in a system dependent header as either:

struct MatchPathSeparator
{
    bool operator()( char ch ) const
    {
        return ch == '/';
    }
};

for Unix, or:

struct MatchPathSeparator
{
    bool operator()( char ch ) const
    {
        return ch == '\\' || ch == '/';
    }
};

for Windows (or something still different for some other unknown system).

EDIT: I missed the fact that he also wanted to suppress the extention. For that, more of the same:

std::string
removeExtension( std::string const& filename )
{
    std::string::const_reverse_iterator
                        pivot
            = std::find( filename.rbegin(), filename.rend(), '.' );
    return pivot == filename.rend()
        ? filename
        : std::string( filename.begin(), pivot.base() - 1 );
}

The code is a little bit more complex, because in this case, the base of the reverse iterator is on the wrong side of where we want to cut. (Remember that the base of a reverse iterator is one behind the character the iterator points to.) And even this is a little dubious: I don't like the fact that it can return an empty string, for example. (If the only '.' is the first character of the filename, I'd argue that you should return the full filename. This would require a little bit of extra code to catch the special case.) }