the shellexecute function will return an error code if the function fails. this can be retrieved using the getlasterror function. if the error code is greater than 32, then the function was successful. if it less than or equal to 32 then an error has occurred. for a complete listing of the error codes refer to the msdn website (link provided in the further reading section).
the easiest way to interpret the error code is with the syserrormessage(getlasterror) function call. this will map the appropriate windows error message returned by the getlasterror api function.
if shellexecute(handle, 'print', pchar('c:\log.txt'), nil, nil, sw_shownormal) <= 32 then
showmessage(syserrormessage(getlasterror));
operation type
the shellexecute function allows for operations to be executed on programs and application objects. in some cases, objects may not be able to respond to an operation type. for example, not all document types support the "print" verb. a list of the commonly supported verbs include:
|
lpoperation value |
result description |
|
edit |
opens a document for editing in an editor. |
|
explore |
explores the folder, using windows explorer, specified by the lpfile parameter. |
|
find |
opens the search form initiating a search starting from the directory specified in the lpfile parameter. |
|
open |
opens the file, application or folder specified by the lpfile parameter. |
|
|
prints the document file specified by lpfile parameter. |
|
null |
more information below |
if null is specified then different functionality will occur depending on the operating system version. the following is an extract from the msdn shellexecute document:
for systems prior to microsoft?windows?2000, the default verb is used if it is valid and available in the registry. if not, the "open" verb is used.
for windows 2000 and later systems, the default verb is used if available. if not, the "open" verb is used. if neither verb is available, the system uses the first verb listed in the registry.
if i use the "open" verb on a .pas file, nothing happens. if i use null instead, then the .pas file will be opened in delphi. the registry defines the application that is associated with the .pas file.
show command
the shellexecute requires the nshowcmd type. this represents how the new window will be displayed when it is created via the shellexecute call.
|
nshowcmd value |
result description |
|
sw_hide |
hides the window and activates another window. |
|
sw_maximize |
maximizes the specified window. |
|
sw_minimize |
minimizes the specified window and activates the next top-level window in the z-order. |
|
sw_restore |
activates and displays the window. if the window is minimized or maximized, windows restores it to its original size and position. an application should specify this flag when restoring a minimized window. |
|
sw_show |
activates the window and displays it in its current size and position. |
|
sw_showdefault |
sets the show state based on the sw_ flag specified in the startupinfo structure passed to the createprocess function by the program that started the application. an application should call showwindow with this flag to set the initial show state of its main window. |
|
sw_showmaximized |
activates the window and displays it as a maximized window. |
|
sw_showminimized |
activates the window and displays it as a minimized window. |
|
sw_showminnoactive |
displays the window as a minimized window. the active window remains active. |
|
sw_showna |
displays the window in its current state. the active window remains active. |
|
sw_shownoactivate |
activates and displays a window. windows restores it to its original size and position. the active window remains active. |
|
sw_shownormal |
activates and displays a window. windows restores it to its original size and position. |
