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C++ Builder has specific Path Manipulation Routines that allow users to edit, extract, get and set drive name, directory name, file name, and file extensions. These methods are combined in Vcl.FileCtrl, System.IOUtils, System.SysUtils libraries. The path manipulation methods are easy to use and simplify the process of getting or setting file path strings. These can be used with other component properties like FileName property of OpenDialog, SaveDialog components.
Let’s see how we can use ExtractFileDir Method to extract a File Directory Name from the File Path String on Windows.
Table of Contents
ExtractFileDir Method
The ExtractFileDir method (System::SysUtils::ExtractFileDir) is a Path Manipulation Routine that extracts the drive and directory parts from the FileName. The resulting string is a directory name suitable for passing to the CreateDir, GetCurrentDir, RemoveDir, and SetCurrentDir functions. This string is empty if FileName contains no drive and directory parts. Note that this function works for multi-byte character systems (MBCS) and returns UnicodeString which is default for String in C++Builder 10+ versions.
Here is the ExtractFileDir C++ syntax
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System::UnicodeString __fastcall ExtractFileDir(const System::UnicodeString FileName); // overload |
Here is a simple C++ example of how to use the ExtractFileDir method
We can separate drives and folders in a path string with “\\” to define single \ and we can extract directory name as below,
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String dir = ExtractFileDir( L"D:\\MainFolder\\SubFolder\\myimage.jpg" ); |
the output dir string will be “D:\MainFolder\SubFolder”.
Here is a simple full C++ Builder VCL Example of using the ExtractFileDir method
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#include <vcl.h> #pragma hdrstop #include "Unit1.h" //--------------------------------------------------------------------------- #pragma package(smart_init) #pragma resource "*.dfm" TForm1 *Form1; //--------------------------------------------------------------------------- __fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) { String str = L"D:\\MainFolder\\SubFolder\\myimage.jpg"; String dir ; dir = ExtractFileDir( str ); ShowMessage( L"Path: " + dir ); } |
The ShowMessage() command will extract and display drive and folders from this string as below,
We can easily use this method with the OpenDialog, SaveDialog components or with the string properties of other components. Here is the C++ Builder VCL Example,
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#include <vcl.h> #pragma hdrstop #include "Unit1.h" //--------------------------------------------------------------------------- #pragma package(smart_init) #pragma resource "*.dfm" TForm1 *Form1; //--------------------------------------------------------------------------- __fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) { } //--------------------------------------------------------------------------- void __fastcall TForm1::Button1Click(TObject *Sender) { OpenDialog1->Execute(); String dir = ExtractFileDir( OpenDialog1->FileName ); ShowMessage( L"Path:" + dir); } |
RAD Studio C++ Builder is a great environment for learning to use C++ and is also powerful enough for all your professional and beginner development needs.
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