processes
CreateProcess QuickInfo Overview Group
The CreateProcess function creates a new process and its primary thread. =
The new
process executes the specified executable file.
BOOL CreateProcess(
LPCTSTR lpApplicationName, // pointer to name of executable module
LPTSTR lpCommandLine, // pointer to command line string
LPSECURITY_ATTRIBUTES lpProcessAttributes, // pointer to process sec=
urity
attributes
LPSECURITY_ATTRIBUTES lpThreadAttributes, // pointer to thread secu=
rity
attributes
BOOL bInheritHandles, // handle inheritance flag
DWORD dwCreationFlags, // creation flags
LPVOID lpEnvironment, // pointer to new environment block
LPCTSTR lpCurrentDirectory, // pointer to current directory n=
ame
LPSTARTUPINFO lpStartupInfo, // pointer to STARTUPINFO
LPPROCESS_INFORMATION lpProcessInformation // pointer to
PROCESS_INFORMATION
);
Parameters
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 execut=
e.
The string can specify a partial name. In that case, the function uses th=
e current drive
and current directory to complete the specification.
The lpApplicationName parameter can be NULL. In that case, the module nam=
e 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 oth=
er type of
module (for example, MS-DOS or OS/2) if the appropriate subsystem is avai=
lable on
the local computer.
Windows NT : If the executable module is a 16-bit application, lpApplicat=
ionName
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 ex=
ecute.
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, *lpApplicationN=
ame
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 arg=
c and argv
arguments.
If lpApplicationName is NULL, the first white space-delimited token of th=
e command
line specifies the module name. If the filename does not contain an exten=
sion, .EXE is
assumed. If the filename ends in a period (.) with no extension, or the f=
ilename
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 GetSyst=
emDirectory
function to get the path of this directory.
Windows NT: The 32-bit Windows system directory. Use the GetSystemDirecto=
ry
function to get the path of this directory. The name of this directory is=
SYSTEM32.
4. Windows NT only: The 16-bit Windows system directory. The=
re 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 functi=
on to get the path
of this directory.
6. The directories that are listed in the PATH environment v=
ariable.
If the process to be created is an MS-DOS - based or Windows-based applic=
ation,
lpCommandLine should be a full command line in which the first element is=
the
application name. Because this also works well for Win32-based applicatio=
ns, it is the
most robust way to set lpCommandLine.
lpProcessAttributes
Points to a SECURITY_ATTRIBUTES structure that specifies the security att=
ributes for
the created process.
If lpProcessAttributes is NULL, the process is created with a default sec=
urity
descriptor, and the resulting handle is not inherited.
lpThreadAttributes
Points to a SECURITY_ATTRIBUTES structure that specifies the security att=
ributes for
the primary thread of the new process. If lpThreadAttributes is NULL, the=
process is
created with a default security descriptor, and the resulting handle is n=
ot inherited.
bInheritHandles
Indicates whether the new process inherits handles from the calling proce=
ss. If TRUE,
each inheritable open handle in the calling process is inherited by the n=
ew process.
Inherited handles have the same value and access privileges as the origin=
al handles.
dwCreationFlags
Specifies additional flags that control the priority class and the creati=
on of the process.
The following creation flags can be specified in any combination, except =
as noted:
Value Meaning
CREATE_DEFAULT_ERROR_MODE
The new process does not inherit the error mode of the calling pr=
ocess. Instead,
CreateProcess gives the new process the current default error mode. An ap=
plication
sets the current default error mode by calling SetErrorMode.This flag is =
particularly
useful for multi-threaded shell applications that run with hard errors di=
sabled. 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 pare=
nt'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 p=
rocess group
includes all processes that are descendants of this root process. The pro=
cess ID of
the new process group is the same as the process ID, which is returned in=
the
lpProcessInformation parameter. Process groups are used by the
GenerateConsoleCtrlEvent function to enable sending a CTRL+C or CTRL+BREA=
K
signal to a group of console processes.
CREATE_SEPARATE_WOW_VDM
This flag is only valid only launching a 16-bit Windows program. =
If set, the new
process is run in a private Virtual DOS Machine (VDM). By default, all 1=
6-bit Windows
programs are run in a single, shared VDM. The advantage of running separ=
ately is that
a crash only kills the single VDM; any other programs running in distinct=
VDMs
continue to function normally. Also, 16-bit Windows applications which a=
re run in
separate VDMs have separate input queues. That means that if one applicat=
ion hangs
momentarily, applications in separate VDMs continue to receive input.
CREATE_SHARED_WOW_VDM
Windows NT: The flag is valid only when launching a 16-bit Window=
s program. 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 s=
tate, and does
not run until the ResumeThread function is called.
CREATE_UNICODE_ENVIRONMENT
If set, the environment block pointed to by lpEnvironment uses Un=
icode 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 w=
ith this flag
set, only the calling thread (the thread that called CreateProcess) can c=
all the
WaitForDebugEvent function.
DEBUG_ONLY_THIS_PROCESS
If not set and the calling process is being debugged, the new pro=
cess 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 occ=
ur.
DETACHED_PROCESS
For console processes, the new process does not have access to th=
e 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_CON=
SOLE
flag.
The dwCreationFlags parameter also controls the new process's priority cl=
ass, 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 i=
s
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:
Priority Meaning
HIGH_PRIORITY_CLASS Indicates a process that performs time-critical t=
asks that
must be executed immediately for it to run correctly. The threads of a hi=
gh-priority
class process preempt the threads of normal-priority or idle-priority cla=
ss processes.
An example is Windows Task List, which must respond quickly when called b=
y the
user, regardless of the load on the operating system. Use extreme care wh=
en using
the high-priority class, because a high-priority class CPU-bound applicat=
ion can use
nearly all available cycles.
IDLE_PRIORITY_CLASS Indicates a process whose threads run only when t=
he
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 schedu=
ling
needs.
REALTIME_PRIORITY_CLASS Indicates a process that has the highest possible
priority. The threads of a real-time priority class process preempt the t=
hreads of all
other processes, including operating system processes performing importan=
t 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-terminat=
ed strings.
Each string is in the form:
name=3Dvalue
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 envir=
onment
block pointed to by lpEnvironment contains Unicode characters, the dwCrea=
tionFlags
field's CREATE_UNICODE_ENVIRONMENT flag will be set. If the block contain=
s 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 t=
erminated 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 d=
irectory 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 s=
hells 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.
Return Value
If the function succeeds, the return value is TRUE.
If the function fails, the return value is FALSE. To get extended error i=
nformation, call
GetLastError.
Remarks
The CreateProcess function is used to run a new program. The WinExec and
LoadModule functions are still available, but they are implemented as cal=
ls to
CreateProcess.
In addition to creating a process, CreateProcess also creates a thread ob=
ject. The
thread is created with an initial stack whose size is described in the im=
age header of
the specified program's executable file. The thread begins execution at t=
he image's
entry point.
The new process and the new thread handles are created with full access r=
ights. For
either handle, if a security descriptor is not provided, the handle can b=
e used in any
function that requires an object handle of that type. When a security des=
criptor is
provided, an access check is performed on all subsequent uses of the hand=
le before
access is granted. If the access check denies access, the requesting proc=
ess is not
able to use the handle to gain access to the thread.
The process is assigned a 32-bit process identifier. The ID is valid unti=
l the process
terminates. It can be used to identify the process, or specified in the O=
penProcess
function to open a handle to the process. The initial thread in the proce=
ss is also
assigned a 32-bit thread identifier. The ID is valid until the thread ter=
minates and can
be used to uniquely identify the thread within the system. These identifi=
ers are
returned in the PROCESS_INFORMATION structure.
When specifying an application name in the lpApplicationName or lpCommand=
Line
strings, it doesn't matter whether the application name includes the file=
name
extension, with one exception: an MS-DOS - based or Windows-based applica=
tion
whose filename extension is .COM must include the .COM extension.
The calling thread can use the WaitForInputIdle function to wait until th=
e new process
has finished its initialization and is waiting for user input with no inp=
ut pending. This
can be useful for synchronization between parent and child processes, bec=
ause
CreateProcess returns without waiting for the new process to finish its i=
nitialization.
For example, the creating process would use WaitForInputIdle before tryin=
g to find a
window associated with the new process.
The preferred way to shut down a process is by using the ExitProcess func=
tion,
because this function notifies all dynamic-link libraries (DLLs) attached=
to the process
of the approaching termination. Other means of shutting down a process do=
not notify
the attached DLLs. Note that when a thread calls ExitProcess, other threa=
ds of the
process are terminated without an opportunity to execute any additional c=
ode
(including the thread termination code of attached DLLs).
ExitProcess, ExitThread, CreateThread, CreateRemoteThread, and a process =
that is
starting (as the result of a call by CreateProcess) are serialized betwee=
n each other
within a process. Only one of these events can happen in an address space=
at a time.
This means the following restrictions hold:
=B7 During process startup and DLL initialization routines, new thr=
eads can be created,
but they do not begin execution until DLL initialization is done for the =
process.
=B7 Only one thread in a process can be in a DLL initialization or =
detach routine at a
time.
=B7 The ExitProcess function does not return until no threads are i=
n their DLL
initialization or detach routines.
The created process remains in the system until all threads within the pr=
ocess have
terminated and all handles to the process and any of its threads have bee=
n closed
through calls to CloseHandle. The handles for both the process and the ma=
in thread
must be closed through calls to CloseHandle. If these handles are not nee=
ded, it is
best to close them immediately after the process is created.
When the last thread in a process terminates, the following events occur:
=B7 All objects opened by the process are implicitly closed.
=B7 The process's termination status (which is returned by GetExitC=
odeProcess)
changes from its initial value of STILL_ACTIVE to the termination status =
of the last
thread to terminate.
=B7 The thread object of the main thread is set to the signaled sta=
te, satisfying any
threads that were waiting on the object.
=B7 The process object is set to the signaled state, satisfying any=
threads that were
waiting on the object.
If the current directory on drive C is \MSVC\MFC, there is an environment=
variable
called =3DC: whose value is C:\MSVC\MFC. As noted in the previous descrip=
tion of
lpEnvironment, such current directory information for a system's drives d=
oes not
automatically propagate to a new process when the CreateProcess function'=
s
lpEnvironment parameter is non-NULL. An application must manually pass th=
e current
directory information to the new process. To do so, the application must =
explicitly
create the =3DX environment variable strings, get them into alphabetical =
order (because
Windows NT and Windows 95 use a sorted environment), and then put them in=
to the
environment block specified by lpEnvironment. Typically, they will go at =
the front of the
environment block, due to the previously mentioned environment block sort=
ing.
One way to obtain the current directory variable for a drive X is to call
GetFullPathName("X:",. .). That avoids an application having to scan the =
environment
block. If the full path returned is X:\, there is no need to pass that va=
lue on as
environment data, since the root directory is the default current directo=
ry for drive X of a
new process.
The handle returned by the CreateProcess function has PROCESS_ALL_ACCESS
access to the process object.
When a process is created with CREATE_NEW_PROCESS_GROUP specified, an
implicit call to SetConsoleCtrlHandler(NULL,TRUE) is made on behalf of th=
e new
process; this means that the new process has CTRL-C disabled. This lets g=
ood shells
handle CTRL-C themselves, and selectively pass that signal on to sub-proc=
esses.
CTRL-BREAK is not disabled, and may be used to interrupt the process/proc=
ess
group.
The current directory specified by the lpcurrentDirectory parameter is th=
e current
directory for the child process. The current directory specified in item =
2 under the
lpCommandLine parameter is the current directory for the parent process.
See Also
AllocConsole, CloseHandle, CreateRemoteThread, CreateThread, ExitProcess,
ExitThread, GenerateConsoleCtrlEvent, GetCommandLine, GetEnvironmentStrin=
gs,
GetExitCodeProcess, GetFullPathName, GetStartupInfo, GetSystemDirectory,
GetWindowsDirectory, LoadModule, OpenProcess, PROCESS_INFORMATION,
ResumeThread, SECURITY_ATTRIBUTES, SetConsoleCtrlHandler, SetErrorMode,
STARTUPINFO, TerminateProcess, WaitForInputIdle, WaitForDebugEvent, WinEx=
ec
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