C++ Builder has specific Path Manipulation Routines that allows user to edit, extract, get and set drive name, directory name, file name, file extensions, .. etc, and these methods are combined in Vcl.FileCtrl, System.IOUtils, System.SysUtils libraries. These path manipulation methods are easy to use and easy to get or set file path strings in that operating system. These can be used with other component properties like FileName property of OpenDialog, SaveDialog components.
By learning how to use ChangeFileExt to change the extension of a file from given a file path String on Windows, and how to compile c++ in windows. It will help you to easily build C++ applications.
Table of Contents
Use the ChangeFileExt method
ChangeFileExt (System::SysUtils::ChangeFileExt) is a Path Manipulation Routine that creates a new file name string changes the extension of a file name. ChangeFileExt takes the file name passed in FileName and changes the extension of the file name to the extension passed in Extension. Extension specifies the new extension, including the initial dot character.
ChangeFileExt does not rename the actual file, it just creates a new file name string. Note that this function works with multi-byte character sets (MBCS) that means it uses UnicodeStrings.
Here is the ChangeFileExt method’s syntax
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System::UnicodeString __fastcall ChangeFileExt(const System::UnicodeString FileName, const System::UnicodeString Extension); // overload |
A simple example of how to use the ChangeFileExt method in C++
We should use L”” literal for the UnicodeStrings and we can separate drives and folders in a path string with “\\” to define single \ and we can get new file name with extension change from a given file path string as below,
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String newname = ChangeFileExt( L"D:\\MainFolder\\SubFolder\\myimage.jpg", L".gif"); ShowMessage(newname); |
Note that again this ChangeFileExt method does not rename the actual file.
Here is the simple full 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) { String str = L"D:\\MainFolder\\SubFolder\\myimage.jpg"; String newname = ChangeFileExt( str, L".gif"); ShowMessage( newname ); // Now we have new name we can ask or change to this name } |
We can use this method with file name strings of any components. For example we can use this with OpenDialog. We can use bool=RenameFile(old, new) Method to rename the selected file with a new extension as below,
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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) { if( OpenDialog1->Execute() ) { String newname = ChangeFileExt( OpenDialog1->FileName, L".gif"); if( RenameFile( OpenDialog1->FileName, newname ) ) ShowMessage( OpenDialog1->FileName + L"renamed to" + newname ); else ShowMessage( "Unable to rename "+OpenDialog1->FileName); } } |
In this example, user selects a file by using OpenDialog file browser and it generates a new file name string with a given extension. Then we change its name to this new name with new extension.
C++ Builder is the easiest and fastest C and C++ IDE for building simple or professional applications on the Windows, MacOS, iOS & Android operating systems. It is also easy for beginners to learn with its wide range of samples, tutorials, help files, and LSP support for code. RAD Studio’s C++ Builder version comes with the award-winning VCL framework for high-performance native Windows apps and the powerful FireMonkey (FMX) framework for cross-platform UIs.
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