Checking if file is in useA few days ago I was asked how to tell if a given file is already being used by another application. Finding out if a file, given its name, is in use (open), is pretty simple. The process consists in trying to open the file for Exclusive Read/Write access. If the file is already in use, it will be locked (by the calling process) for exclusive access, and the call will fail. Please note that some application do not lock the file when using it. One clear example of this is NOTEPAD. If you open a TXT file in Notepad, the file will not be locked, so the function below will report the file as not being in use.The function below, IsFileInUse will return true if the file is locked for exclusive access. As it uses CreateFile, it would also fail if the file doesn't exists. In my opinion, a file that doesn't exist is a file that is not in use. That's why I added the FileExists call in the function. Anyway, here's the function:
function IsFileInUse(fName : string) : boolean;
var
HFileRes : HFILE;
begin
Result := false;
if not FileExists(fName) then
exit;
HFileRes := CreateFile(pchar(fName), GENERIC_READ or GENERIC_WRITE,
0 {this is the trick!}, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
Result := (HFileRes = INVALID_HANDLE_VALUE);
if not Result then
CloseHandle(HFileRes);
end;
NOTE: The function will return false if the specified file doesn't exist, meaning that it is not in use and can be used for something else.
function IsFileInUse(fName : string) : boolean;
var
HFileRes : HFILE;
begin
Result := false;
if not FileExists(fName) then
exit;
HFileRes := CreateFile(pchar(fName), GENERIC_READ or GENERIC_WRITE,
0 {this is the trick!}, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
Result := (HFileRes = INVALID_HANDLE_VALUE);
if not Result then
CloseHandle(HFileRes);
end;
NOTE: The function will return false if the specified file doesn't exist, meaning that it is not in use and can be used for something else.
ShellApi;function DeleteFileWithUndo(sFileName : string ) : boolean;
var
fos : TSHFileOpStruct;
begin
FillChar( fos, SizeOf( fos ), 0 );
with fos do
begin
Wnd := application.handle;
wFunc := FO_DELETE;
pFrom := PChar( sFileName );
fFlags := FOF_ALLOWUNDO or FOF_NOCONFIRMATION or FOF_SILENT;
end;
Result := ( 0 = ShFileOperation( fos ) );
end;
procedure TForm1.Button1Click(Sender: TObject);
var
i : integer;
begin
for i := 0 to ComponentCount-1 do
begin
if( Components[ i ] is TEdit )then
begin
(Components[ i ] as TEdit).Text := '';
end;
end;
end;
sKey, sItem, sDefVal : string )
: string;
var
reg : TRegIniFile;
begin
reg := TRegIniFile.Create( sKey );
Result := reg.ReadString(
'', sItem, sDefVal );
reg.Free;
end;procedure SaveStringToRegistry( sKey, sItem, sVal : string );
var
reg : TRegIniFile;
begin
reg := TRegIniFile.Create( sKey );
reg.WriteString(
'', sItem, sVal + #0 );
reg.Free;
end;
all of english
我晕了，我晕了
all of english
我晕了，我晕了
slTemp: IShellLink;
pfTemp: IPersistFile;
sTarget: String; { This is the path and name of the file that the
shortcut is to point too }
sIconFile : String; { This is the path and name of the file that contains
the icon (it can be an .exe or .ico file) }
iIconIndex : Integer { The index of which icon to use in the specified file }
sName : String { The name for the shortcut including the path}begin
// initialize the COM engine
CoInitialize(nil);
try
// create an uninitialized IShellLink (a shortcut)
if CoCreateInstance(CLSID_ShellLink,
nil,
CLSCTX_INPROC_SERVER,
IShellLink, slTemp) = S_OK then
begin
slTemp.SetPath(PChar(sTarget));
slTemp.SetIconLocation(PChar(sIconFile), iIconIndex);
//Get an IPersistFile interface (needed to specify the name of the Shortcut)
if slTemp.QueryInterface(IPersistFile, pfTemp) = S_OK then
if pfTemp.Save(StringToOleStr(sName), True) <> S_OK then
ShowMessage('could not save the shortcut');
// do not Release slTemp, it is done automatically by Delphi
end;
// deinitialize COM
finally
CoUninitialize;
end;
end;
A function to execute a DOS or Win32 consoloe mode application and wait for it to close before continuing. Input for the app can be directed from a file, and the output will be redirected to a file.
uses
Controls, Windows, SysUtils, Forms;{---------------------------CreateDOSProcessRedirected--------------------------
Description : executes a (DOS!) app defined in the CommandLine parameter
redirected to take input from InputFile (optional) and give
output to OutputFile
Result : True on success
Parameters : CommandLine : the command line for app, including full path
InputFile : the ascii file where from the app takes input,
empty if no input needed/required.
OutputFile : the ascii file to which the output is redirected
ErrMsg : additional error message string. Can be empty
Error checking : YES
Target : Delphi 2, 3, 4
Author : Theodoros Bebekis, email [email protected]
Notes :
Example call : CreateDOSProcessRedirected('C:\MyDOSApp.exe',
'C:\InputPut.txt',
'C:\OutPut.txt',
'Please, record this message')
-------------------------------------------------------------------------------}
function CreateDOSProcessRedirected(const CommandLine, InputFile, OutputFile,
ErrMsg :string): boolean;
const
ROUTINE_ID = '[function: CreateDOSProcessRedirected]';
var
OldCursor : TCursor;
pCommandLine : array[0..MAX_PATH] of char;
pInputFile,
pOutPutFile : array[0..MAX_PATH] of char;
StartupInfo : TStartupInfo;
ProcessInfo : TProcessInformation;
SecAtrrs : TSecurityAttributes;
hAppProcess,
hAppThread,
hInputFile,
hOutputFile : THandle;
begin
Result := FALSE; { check for InputFile existence }
if (InputFile <> '') and (not FileExists(InputFile)) then
raise Exception.CreateFmt(ROUTINE_ID + #10 + #10 +
'Input file * %s *' + #10 +
'does not exist' + #10 + #10 +
ErrMsg, [InputFile]); hAppProcess := 0;
hAppThread := 0;
hInputFile := 0;
hOutputFile := 0; { save the cursor }
OldCursor := Screen.Cursor;
Screen.Cursor := crHourglass; try
{ copy the parameter Pascal strings to null terminated strings }
StrPCopy(pCommandLine, CommandLine);
StrPCopy(pInputFile, InputFile);
StrPCopy(pOutPutFile, OutputFile); { prepare SecAtrrs structure for the CreateFile calls. This SecAttrs
structure is needed in this case because we want the returned handle to
be inherited by child process. This is true when running under WinNT.
As for Win95, the parameter is ignored. }
FillChar(SecAtrrs, SizeOf(SecAtrrs), #0);
SecAtrrs.nLength := SizeOf(SecAtrrs);
SecAtrrs.lpSecurityDescriptor := nil;
SecAtrrs.bInheritHandle := TRUE; if InputFile <> '' then
begin
{ create the appropriate handle for the input file }
hInputFile := CreateFile(
pInputFile, { pointer to name of the file }
GENERIC_READ or GENERIC_WRITE, { access (read-write) mode }
FILE_SHARE_READ or FILE_SHARE_WRITE, { share mode }
@SecAtrrs, { pointer to security attributes }
OPEN_ALWAYS, { how to create }
FILE_ATTRIBUTE_NORMAL
or FILE_FLAG_WRITE_THROUGH, { file attributes }
0); { handle to file with attrs to copy } { is hInputFile a valid handle? }
if hInputFile = INVALID_HANDLE_VALUE then
raise Exception.CreateFmt(ROUTINE_ID + #10 + #10 +
'WinApi function CreateFile returned an invalid handle value' + #10 +
'for the input file * %s *' + #10 + #10 +
ErrMsg, [InputFile]);
end else
{ we aren't using an input file }
hInputFile := 0; { create the appropriate handle for the output file }
hOutputFile := CreateFile(
pOutPutFile, { pointer to name of the file }
GENERIC_READ or GENERIC_WRITE, { access (read-write) mode }
FILE_SHARE_READ or FILE_SHARE_WRITE, { share mode }
@SecAtrrs, { pointer to security attributes }
CREATE_ALWAYS, { how to create }
FILE_ATTRIBUTE_NORMAL
or FILE_FLAG_WRITE_THROUGH, { file attributes }
0 ); { handle to file with attrs to copy } { is hOutputFile a valid handle? }
if hOutputFile = INVALID_HANDLE_VALUE then
raise Exception.CreateFmt(ROUTINE_ID + #10 + #10 +
'WinApi function CreateFile returned an invalid handle value' + #10 +
'for the output file * %s *' + #10 + #10 +
ErrMsg, [OutputFile]); { prepare StartupInfo structure }
FillChar(StartupInfo, SizeOf(StartupInfo), #0);
StartupInfo.cb := SizeOf(StartupInfo);
StartupInfo.dwFlags := STARTF_USESHOWWINDOW or STARTF_USESTDHANDLES;
StartupInfo.wShowWindow := SW_HIDE;
StartupInfo.hStdOutput := hOutputFile;
StartupInfo.hStdInput := hInputFile; { create the app }
Result := CreateProcess(
NIL, { pointer to name of executable module }
pCommandLine, { pointer to command line string }
NIL, { pointer to process security attributes }
NIL, { pointer to thread security attributes }
TRUE, { handle inheritance flag }
HIGH_PRIORITY_CLASS, { creation flags }
NIL, { pointer to new environment block }
NIL, { pointer to current directory name }
StartupInfo, { pointer to STARTUPINFO }
ProcessInfo); { pointer to PROCESS_INF } { wait for the app to finish its job and take the handles to free them later }
if Result then
begin
WaitforSingleObject(ProcessInfo.hProcess, INFINITE);
hAppProcess := ProcessInfo.hProcess;
hAppThread := ProcessInfo.hThread;
end else
raise Exception.Create(ROUTINE_ID + #10 + #10 +
'Function failure' + #10 + #10 + ErrMsg); finally
{ close the handles
Kernel objects, like the process and the files we created in this case,
are maintained by a usage count.
So, for cleaning up purposes we have to close the handles
to inform the system that we don't need the objects anymore }
if hOutputFile <> 0 then
CloseHandle(hOutputFile);
if hInputFile <> 0 then
CloseHandle(hInputFile);
if hAppThread <> 0 then
CloseHandle(hAppThread);
if hAppProcess <> 0 then
CloseHandle(hAppProcess);
{ restore the old cursor }
Screen.Cursor:= OldCursor;
end;
end; { CreateDOSProcessRedirected }
A function to execute a DOS or Win32 consoloe mode application and wait for it to close before continuing. Input for the app can be directed from a file, and the output will be redirected to a file.
uses
Controls, Windows, SysUtils, Forms;{---------------------------CreateDOSProcessRedirected--------------------------
Description : executes a (DOS!) app defined in the CommandLine parameter
redirected to take input from InputFile (optional) and give
output to OutputFile
Result : True on success
Parameters : CommandLine : the command line for app, including full path
InputFile : the ascii file where from the app takes input,
empty if no input needed/required.
OutputFile : the ascii file to which the output is redirected
ErrMsg : additional error message string. Can be empty
Error checking : YES
Target : Delphi 2, 3, 4
Author : Theodoros Bebekis, email [email protected]
Notes :
Example call : CreateDOSProcessRedirected('C:\MyDOSApp.exe',
'C:\InputPut.txt',
'C:\OutPut.txt',
'Please, record this message')
-------------------------------------------------------------------------------}
function CreateDOSProcessRedirected(const CommandLine, InputFile, OutputFile,
ErrMsg :string): boolean;
const
ROUTINE_ID = '[function: CreateDOSProcessRedirected]';
var
OldCursor : TCursor;
pCommandLine : array[0..MAX_PATH] of char;
pInputFile,
pOutPutFile : array[0..MAX_PATH] of char;
StartupInfo : TStartupInfo;
ProcessInfo : TProcessInformation;
SecAtrrs : TSecurityAttributes;
hAppProcess,
hAppThread,
hInputFile,
hOutputFile : THandle;
begin
Result := FALSE; { check for InputFile existence }
if (InputFile <> '') and (not FileExists(InputFile)) then
raise Exception.CreateFmt(ROUTINE_ID + #10 + #10 +
'Input file * %s *' + #10 +
'does not exist' + #10 + #10 +
ErrMsg, [InputFile]); hAppProcess := 0;
hAppThread := 0;
hInputFile := 0;
hOutputFile := 0; { save the cursor }
OldCursor := Screen.Cursor;
Screen.Cursor := crHourglass; try
{ copy the parameter Pascal strings to null terminated strings }
StrPCopy(pCommandLine, CommandLine);
StrPCopy(pInputFile, InputFile);
StrPCopy(pOutPutFile, OutputFile); { prepare SecAtrrs structure for the CreateFile calls. This SecAttrs
structure is needed in this case because we want the returned handle to
be inherited by child process. This is true when running under WinNT.
As for Win95, the parameter is ignored. }
FillChar(SecAtrrs, SizeOf(SecAtrrs), #0);
SecAtrrs.nLength := SizeOf(SecAtrrs);
SecAtrrs.lpSecurityDescriptor := nil;
SecAtrrs.bInheritHandle := TRUE; if InputFile <> '' then
begin
{ create the appropriate handle for the input file }
hInputFile := CreateFile(
pInputFile, { pointer to name of the file }
GENERIC_READ or GENERIC_WRITE, { access (read-write) mode }
FILE_SHARE_READ or FILE_SHARE_WRITE, { share mode }
@SecAtrrs, { pointer to security attributes }
OPEN_ALWAYS, { how to create }
FILE_ATTRIBUTE_NORMAL
or FILE_FLAG_WRITE_THROUGH, { file attributes }
0); { handle to file with attrs to copy } { is hInputFile a valid handle? }
if hInputFile = INVALID_HANDLE_VALUE then
raise Exception.CreateFmt(ROUTINE_ID + #10 + #10 +
'WinApi function CreateFile returned an invalid handle value' + #10 +
'for the input file * %s *' + #10 + #10 +
ErrMsg, [InputFile]);
end else
{ we aren't using an input file }
hInputFile := 0; { create the appropriate handle for the output file }
hOutputFile := CreateFile(
pOutPutFile, { pointer to name of the file }
GENERIC_READ or GENERIC_WRITE, { access (read-write) mode }
FILE_SHARE_READ or FILE_SHARE_WRITE, { share mode }
@SecAtrrs, { pointer to security attributes }
CREATE_ALWAYS, { how to create }
FILE_ATTRIBUTE_NORMAL
or FILE_FLAG_WRITE_THROUGH, { file attributes }
0 ); { handle to file with attrs to copy } { is hOutputFile a valid handle? }
if hOutputFile = INVALID_HANDLE_VALUE then
raise Exception.CreateFmt(ROUTINE_ID + #10 + #10 +
'WinApi function CreateFile returned an invalid handle value' + #10 +
'for the output file * %s *' + #10 + #10 +
ErrMsg, [OutputFile]); { prepare StartupInfo structure }
FillChar(StartupInfo, SizeOf(StartupInfo), #0);
StartupInfo.cb := SizeOf(StartupInfo);
StartupInfo.dwFlags := STARTF_USESHOWWINDOW or STARTF_USESTDHANDLES;
StartupInfo.wShowWindow := SW_HIDE;
StartupInfo.hStdOutput := hOutputFile;
StartupInfo.hStdInput := hInputFile; { create the app }
Result := CreateProcess(
NIL, { pointer to name of executable module }
pCommandLine, { pointer to command line string }
NIL, { pointer to process security attributes }
NIL, { pointer to thread security attributes }
TRUE, { handle inheritance flag }
HIGH_PRIORITY_CLASS, { creation flags }
NIL, { pointer to new environment block }
NIL, { pointer to current directory name }
StartupInfo, { pointer to STARTUPINFO }
ProcessInfo); { pointer to PROCESS_INF } { wait for the app to finish its job and take the handles to free them later }
if Result then
begin
WaitforSingleObject(ProcessInfo.hProcess, INFINITE);
hAppProcess := ProcessInfo.hProcess;
hAppThread := ProcessInfo.hThread;
end else
raise Exception.Create(ROUTINE_ID + #10 + #10 +
'Function failure' + #10 + #10 + ErrMsg); finally
{ close the handles
Kernel objects, like the process and the files we created in this case,
are maintained by a usage count.
So, for cleaning up purposes we have to close the handles
to inform the system that we don't need the objects anymore }
if hOutputFile <> 0 then
CloseHandle(hOutputFile);
if hInputFile <> 0 then
CloseHandle(hInputFile);
if hAppThread <> 0 then
CloseHandle(hAppThread);
if hAppProcess <> 0 then
CloseHandle(hAppProcess);
{ restore the old cursor }
Screen.Cursor:= OldCursor;
end;
end; { CreateDOSProcessRedirected }
The ShellApi unit contains some good functions. Among the more exotic are this one, ShellAbout. With this function you can open the default Windows About Box with your own text:
uses
ShellApi;begin
ShellAbout( self.Handle, pChar('This is my header'),
pChar('This is my copyright'), HICON(nil)
);
end;If you wish to include your own icon, let HICON(nil) point to a icon handle. When pointing to nil the default Windows ison is used.
The ShellApi unit contains some good functions. Among the more exotic are this one, ShellAbout. With this function you can open the default Windows About Box with your own text:
uses
ShellApi;begin
ShellAbout( self.Handle, pChar('This is my header'),
pChar('This is my copyright'), HICON(nil)
);
end;If you wish to include your own icon, let HICON(nil) point to a icon handle. When pointing to nil the default Windows ison is used.