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CreateProcess The CreateProcess function creates a new process and its primary thread. The new process executes the specified executable file.
VB4-32,5,6
Declare Function CreateProcess Lib "kernel32" Alias "CreateProcessA" (ByVal lpApplicationName As String, ByVal lpCommandLine As String, lpProcessAttributes As SECURITY_ATTRIBUTES, lpThreadAttributes As SECURITY_ATTRIBUTES, ByVal bInheritHandles As Long, ByVal dwCreationFlags As Long, lpEnvironment As Any, ByVal lpCurrentDriectory As String, lpStartupInfo As STARTUPINFO, lpProcessInformation As PROCESS_INFORMATION) As Long |
VB.NET
System.Diagnostics.Process |
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Operating Systems Supported |
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Requires Windows NT 3.1 or later; Requires Windows 95 or later |
- lpApplicationName
Pointer to a null-terminated string that specifies the module to execute.
The string can specify the full path and filename of the module to execute.
The string can specify a partial name. In that case, the function uses the current drive and current directory to complete the specification.
The lpApplicationName parameter can be NULL. In that case, the module name must be the first white space-delimited token in the lpCommandLine string.
The specified module can be a Win32-based application. It can be some other type of module (for example, MS-DOS or OS/2) if the appropriate subsystem is available on the local computer.
Windows NT: If the executable module is a 16-bit application, lpApplicationName should be NULL, and the string pointed to by lpCommandLine should specify the executable module. A 16-bit application is one that executes as a VDM or WOW process.
- lpCommandLine
Pointer to a null-terminated string that specifies the command line to execute.
The lpCommandLine parameter can be NULL. In that case, the function uses the string pointed to by lpApplicationName as the command line.
If both lpApplicationName and lpCommandLine are non-NULL, *lpApplicationName specifies the module to execute, and *lpCommandLine specifies the command line. The new process can use GetCommandLine to retrieve the entire command line. C runtime processes can use the argc and argv arguments.
If lpApplicationName is NULL, the first white space-delimited token of the command line specifies the module name. If the filename does not contain an extension, .EXE is assumed. If the filename ends in a period (.) with no extension, or the filename contains a path, .EXE is not appended. If the filename does not contain a directory path, Windows searches for the executable file in the following sequence:
1. The directory from which the application loaded.
2. The current directory for the parent process.
3. Windows 95: The Windows system directory. Use the GetSystemDirectory function to get the path of this directory.
Windows NT: The 32-bit Windows system directory. Use the GetSystemDirectory function to get the path of this directory. The name of this directory is SYSTEM32.
4. Windows NT: The 16-bit Windows system directory. There is no Win32 function that obtains the path of this directory, but it is searched. The name of this directory is SYSTEM.
5. The Windows directory. Use the GetWindowsDirectory function to get the path of this directory.
6. The directories that are listed in the PATH environment variable.
If the process to be created is an MS-DOS - based or Windows-based application, lpCommandLine should be a full command line in which the first element is the application name. Because this also works well for Win32-based applications, it is the most robust way to set lpCommandLine.
- lpProcessAttributes
Pointer to a SECURITY_ATTRIBUTES structure that determines whether the returned handle can be inherited by child processes. If lpProcessAttributes is NULL, the handle cannot be inherited.
Windows NT: The lpSecurityDescriptor member of the structure specifies a security descriptor for the new process. If lpProcessAttributes is NULL, the process gets a default security descriptor.
Windows 95: The lpSecurityDescriptor member of the structure is ignored.
- lpThreadAttributes
Pointer to a SECURITY_ATTRIBUTES structure that determines whether the returned handle can be inherited by child processes. If lpThreadAttributes is NULL, the handle cannot be inherited.
Windows NT: The lpSecurityDescriptor member of the structure specifies a security descriptor for the main thread. If lpThreadAttributes is NULL, the thread gets a default security descriptor.
Windows 95: The lpSecurityDescriptor member of the structure is ignored.
- bInheritHandles
Indicates whether the new process inherits handles from the calling process. If TRUE, each inheritable open handle in the calling process is inherited by the new process. Inherited handles have the same value and access privileges as the original handles.
- dwCreationFlags
Specifies additional flags that control the priority class and the creation of the process. The following creation flags can be specified in any combination, except as noted:
CREATE_DEFAULT_ERROR_MODE
The new process does not inherit the error mode of the calling process. Instead, CreateProcess gives the new process the current default error mode. An application sets the current default error mode by calling SetErrorMode.
This flag is particularly useful for multi-threaded shell applications that run with hard errors disabled.
The default behavior for CreateProcess is for the new process to inherit the error mode of the caller. Setting this flag changes that default behavior.
CREATE_NEW_CONSOLE
The new process has a new console, instead of inheriting the parent’s console. This flag cannot be used with the DETACHED_PROCESS flag.
CREATE_NEW_PROCESS_GROUP
The new process is the root process of a new process group. The process group includes all processes that are descendants of this root process. The process identifier of the new process group is the same as the process identifier, which is returned in the lpProcessInformation parameter. Process groups are used by the GenerateConsoleCtrlEvent function to enable sending a CTRL+C or CTRL+BREAK signal to a group of console processes.
CREATE_SEPARATE_WOW_VDM
Windows NT only: This flag is valid only when starting a 16-bit Windows-based application. If set, the new process is run in a private Virtual DOS Machine (VDM). By default, all 16-bit Windows-based applications are run as threads in a single, shared VDM. The advantage of running separately is that a crash only kills the single VDM; any other programs running in distinct VDMs continue to function normally. Also, 16-bit Windows-based applications that are run in separate VDMs have separate input queues. That means that if one application hangs momentarily, applications in separate VDMs continue to receive input.
CREATE_SHARED_WOW_VDM
Windows NT only: The flag is valid only when starting a 16-bit Windows-based application. If the DefaultSeparateVDM switch in the Windows section of WIN.INI is TRUE, this flag causes the CreateProcess function to override the switch and run the new process in the shared Virtual DOS Machine.
CREATE_SUSPENDED
The primary thread of the new process is created in a suspended state, and does not run until the ResumeThread function is called.
CREATE_UNICODE_ENVIRONMENT
If set, the environment block pointed to by lpEnvironment uses Unicode characters. If clear, the environment block uses ANSI characters.
DEBUG_PROCESS
If this flag is set, the calling process is treated as a debugger, and the new process is a process being debugged. The system notifies the debugger of all debug events that occur in the process being debugged.
If you create a process with this flag set, only the calling thread (the thread that called CreateProcess) can call the WaitForDebugEvent function.
DEBUG_ONLY_THIS_PROCESS
If not set and the calling process is being debugged, the new process becomes another process being debugged by the calling process’s debugger. If the calling process is not a process being debugged, no debugging-related actions occur.
DETACHED_PROCESS
For console processes, the new process does not have access to the console of the parent process. The new process can call the AllocConsole function at a later time to create a new console. This flag cannot be used with the CREATE_NEW_CONSOLE flag.
The dwCreationFlags parameter also controls the new process’s priority class, which is used in determining the scheduling priorities of the process’s threads. If none of the following priority class flags is specified, the priority class defaults to NORMAL_PRIORITY_CLASS unless the priority class of the creating process is IDLE_PRIORITY_CLASS. In this case the default priority class of the child process is IDLE_PRIORITY_CLASS. One of the following flags can be specified:
HIGH_PRIORITY_CLASS
Indicates a process that performs time-critical tasks that must be executed immediately for it to run correctly. The threads of a high-priority class process preempt the threads of normal-priority or idle-priority class processes. An example is Windows Task List, which must respond quickly when called by the user, regardless of the load on the operating system. Use extreme care when using the high-priority class, because a high-priority class CPU-bound application can use nearly all available cycles.
IDLE_PRIORITY_CLASS
Indicates a process whose threads run only when the system is idle and are preempted by the threads of any process running in a higher priority class. An example is a screen saver. The idle priority class is inherited by child processes.
NORMAL_PRIORITY_CLASS
Indicates a normal process with no special scheduling needs.
REALTIME_PRIORITY_CLASS
Indicates a process that has the highest possible priority. The threads of a real-time priority class process preempt the threads of all other processes, including operating system processes performing important tasks. For example, a real-time process that executes for more than a very brief interval can cause disk caches not to flush or cause the mouse to be unresponsive.
- lpEnvironment
Points to an environment block for the new process. If this parameter is NULL, the new process uses the environment of the calling process.
An environment block consists of a null-terminated block of null-terminated strings. Each string is in the form:
name=value
Because the equal sign is used as a separator, it must not be used in the name of an environment variable.
If an application provides an environment block, rather than passing NULL for this parameter, the current directory information of the system drives is not automatically propagated to the new process. For a discussion of this situation and how to handle it, see the following Remarks section.
An environment block can contain Unicode or ANSI characters. If the environment block pointed to by lpEnvironment contains Unicode characters, the dwCreationFlags field’s CREATE_UNICODE_ENVIRONMENT flag will be set. If the block contains ANSI characters, that flag will be clear.
Note that an ANSI environment block is terminated by two zero bytes: one for the last string, one more to terminate the block. A Unicode environment block is terminated by four zero bytes: two for the last string, two more to terminate the block.
- lpCurrentDirectory
Points to a null-terminated string that specifies the current drive and directory for the child process. The string must be a full path and filename that includes a drive letter. If this parameter is NULL, the new process is created with the same current drive and directory as the calling process. This option is provided primarily for shells that need to start an application and specify its initial drive and working directory.
- lpStartupInfo
Points to a STARTUPINFO structure that specifies how the main window for the new process should appear.
- lpProcessInformation
Points to a PROCESS_INFORMATION structure that receives identification information about the new process. |
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error information, call GetLastError. |
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