C++ Builder has a lot of specific methods in its SysUtils library that are included in the vcl and fmx libraries. Some of these are grouped as a 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 all 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. We can also check files or directories to see if they exist or not in that given path.
In this post, you’ll learn how to check if a file exists in a folder, whether a file exists or not, and how to check if a drive, directory, or file exists. By learning more about FileExists Method that checks if it exists in that path on Windows, and how to compile c++ in windows. It will help you to easily build C++ applications.
Table of Contents
What is the C++ FileExists method?
The FileExists Method (System::SysUtils::FileExists) is a SysUtils Method in C++ Builder that checks whether a specified file exists. FileExists returns True if the file specified by FileName exists. If the file does not exist, FileExists returns False.
What is the syntax of the C++ FileExists method?
Here is the Syntax of FileExists Method:
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bool __fastcall FileExists(const System::UnicodeString FileName, bool FollowLink = true); |
Note: If the FileName parameter is a symbolic link and the FollowLink parameter is set to True, the method is performed on the target file. If the first condition is True, but the FollowLink parameter is set to False, the symbolic link is used, regardless whether the link is broken (the target file is invalid).
Method behavior if the FileName parameter is a file:
| File Exists | FollowLink | Method result |
|---|---|---|
| YES | True | True |
| YES | False | True |
| NO | True | False |
| NO | False | False |
Method behavior if the FileName parameter is a symbolic link:
| Target Exists | FollowLink | Method result |
|---|---|---|
| YES | True | True |
| YES | False | True |
| NO | True | False |
| NO | False | True |
A simple example of how to use the C++ FileExists() method
FileExist Method returns a Boolean, we can check a file and set the result to a bool as below,
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bool check = FileExists( L"D:\\MainFolder\\SubFolder\\myimage.jpg" ); |
or we can directly set its result to a components value, for example we can use it with a CheckBox (TCheckBox) component as below
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CheckBox1->IsChecked = FileExists( L"D:\\MainFolder\\SubFolder\\myimage.jpg" ); |
A more complete example of how to use the C++ FileExists() method
The most used way is the checking file existence by if clauses and doing actions in that way, For example, here is a full example that checks two different file existence.
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#include <vcl.h> #pragma hdrstop #include "SysUtils_File_Methods_Unit1.h" //--------------------------------------------------------------------------- #pragma package(smart_init) #pragma resource "*.dfm" TForm1 *Form1; //--------------------------------------------------------------------------- __fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) { if ( FileExists( L"C:\\Windows\\System32\\NotePad.exe") ) { ShowMessage("NotePad.exe exists in that path"); } else { ShowMessage("NotePad.exe doesn't exist in that path"); } if ( FileExists( L"C:\\Windows\\System32\\LearnCPlusPlus.exe") ) { ShowMessage("LearnCPlusPlus.exe exists in that path"); } else { ShowMessage("LearnCPlusPlus.exe doesn't exist in that path"); } } |
This method can be used with other component properties like FileName property of OpenDialog, SaveDialog components. For example you can let user browse a file and if that file doesn’t exist then create a new file. Or you can use them to select a folder then you can check your file if it exist or not in that folder. Remember that there is a drive check Note that this method can be used as same as examples above with FMX applications too.
As same as here above, there are a DirectoryExists() method to check directories and FileExists() method to check files. More examples about Path Operations can be found here
Here is the full example about using DriveExists(), DirectoryExists() and FileExists() Methods,
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#include <vcl.h> #include <IOUtils.hpp> #pragma hdrstop #include "SysUtils_File_Methods_Unit1.h" //--------------------------------------------------------------------------- #pragma package(smart_init) #pragma resource "*.dfm" TForm1 *Form1; //--------------------------------------------------------------------------- __fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) { if ( TPath::DriveExists( L"C:\\") ) { ShowMessage("C: Drive exists"); } else { ShowMessage("C: Drive does NOT exist"); } if ( DirectoryExists( L"C:\\Windows\\System32") ) { ShowMessage("Systme32 Folder exists"); } else { ShowMessage("Systme32 Folder doesn't exist"); } if ( FileExists( L"C:\\Windows\\System32\\NotePad.exe") ) { ShowMessage("NotePad.exe File exists in that path"); } else { ShowMessage("NotePad.exe File doesn't exist in that path"); } if ( FileExists( L"C:\\Windows\\System32\\LearnCPlusPlus.exe") ) { ShowMessage("LearnCPlusPlus.exe File exists in that path"); } else { ShowMessage("LearnCPlusPlus.exe File doesn't exist in that path"); } } |
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