Using ShellExecute in Delphi to Launch ApplicationsHow to use ShellExecute functions in Delphi to launch programs and files from your code. Opening files will use the system default editor.
To launch an application or execute a file in Win32 environment we will use the ShellExecute Windows API function. ShellExecute is the code equivalent of a user double clicking a file icon. It causes Windows to work out what application the document file is associated with, launch the program and have it load the document file.
If you pass in a .exe file, it will be launched. If you pass in a .txt file, Windows will work out what application opens this file then launch the application and load the file.
As you will see we can open any type of document from our program without knowing which program is associated with it (this link is defined in the Windows Registry).
Be sure to add ShellApi to your Unit's uses clause.
To Run Notepad
uses ShellApi;
...
ShellExecute(Handle, 'open', 'c:/Windows/notepad.exe', nil, nil, SW_SHOWNORMAL); Open SomeText.txt with Notepad
ShellExecute(Handle,'open', 'c:/windows/notepad.exe','c:/SomeText.txt', nil, SW_SHOWNORMAL); Display the contents of the "DelphiDownload" folder
ShellExecute(Handle,'open', 'c:/DelphiDownload', nil, nil, SW_SHOWNORMAL); Execute a file according to its extension
ShellExecute(Handle, 'open','c:/MyDocuments/Letter.doc',nil,nil,SW_SHOWNORMAL); Open web site or a *.htm file with the default web explorer
ShellExecute(Handle, 'open','http://delphi.about.com',nil,nil, SW_SHOWNORMAL); Send an e-mail with the subject and the message body
var em_subject, em_body, em_mail : string;
begin
em_subject := 'This is the subject line';
em_body := 'Message body text goes here';
em_mail := 'mailto:delphi.guide@about.com?subject=' + em_subject + '&body=' + em_body;
ShellExecute(Handle,'open', PChar(em_mail), nil, nil, SW_SHOWNORMAL);
end; Execute a program and wait until it has finished
The following example uses the ShellExecuteEx API function.
/ Execute the Windows Calculator and pop up
/ a message when the Calc is terminated.
uses ShellApi;
...
var
SEInfo: TShellExecuteInfo;
ExitCode: DWORD;
ExecuteFile, ParamString, StartInString: string;
begin
ExecuteFile:='c:\WindowsCalc.exe';
FillChar(SEInfo, SizeOf(SEInfo), 0);
SEInfo.cbSize := SizeOf(TShellExecuteInfo);
with SEInfo do begin
fMask := SEE_MASK_NOCLOSEPROCESS;
Wnd := Application.Handle;
lpFile := PChar(ExecuteFile);
{
ParamString can contain the
application parameters.
}
/ lpParameters := PChar(ParamString);
{
StartInString specifies the
name of the working directory.
If ommited, the current directory is used.
}
/ lpDirectory := PChar(StartInString);
nShow := SW_SHOWNORMAL;
end;
if ShellExecuteEx(@SEInfo) then begin
repeat
Application.ProcessMessages;
GetExitCodeProcess(SEInfo.hProcess, ExitCode);
until (ExitCode <> STILL_ACTIVE) or
Application.Terminated;
ShowMessage('Calculator terminated');
end
else ShowMessage('Error starting Calc!');
end; 
