Home > Articles > Operating Systems, Server > Microsoft Servers

This chapter is from the book

Process Creation

The fundamental Windows process management function is CreateProcess, which creates a process with a single thread. It is necessary to specify the name of an executable program file as part of the CreateProcess call.

It is common to speak of parent and child processes, but these relationships are not actually maintained by Windows. It is simply convenient to refer to the process that creates a child process as the parent.

CreateProcess has ten parameters to support its flexibility and power. Initially, it is simple to use default values. Just as with CreateFile, it is appropriate to explain all the CreateProcess parameters. Related functions then become easier to understand.

Note first that the function does not return a HANDLE; rather, two separate handles, one each for the process and the thread, are returned in a structure specified in the call. CreateProcess creates a new process with a primary thread. The example programs are always very careful to close both of these handles when they are no longer needed in order to avoid resource leaks; a common defect is to neglect to close the thread handle. Closing a thread handle, for instance, does not terminate the thread; the CloseHandle function only deletes the reference to the thread within the process that called CreateProcess.

BOOL CreateProcess (
   LPCTSTR lpApplicationName,
   LPTSTR lpCommandLine,
   BOOL bInheritHandles,
   DWORD dwCreationFlags,
   LPVOID lpEnvironment,
   LPCTSTR lpCurDir,
   LPSTARTUPINFO lpStartupInfo,

Return: TRUE only if the process and thread are successfully created.


Some parameters require extensive explanations in the following sections, and many are illustrated in the program examples.

lpApplicationName and lpCommandLine (this is an LPTSTR and not an LPCTSTR) together specify the executable program and the command line arguments, as explained in the next section.

lpsaProcess and lpsaThread point to the process and thread security attribute structures. NULL values imply default security and will be used until Chapter 15, which covers Windows security.

bInheritHandles indicates whether the new process inherits copies of the calling process's inheritable open handles (files, mappings, and so on). Inherited handles have the same attributes as the originals and are discussed in detail in a later section.

dwCreationFlags combines several flags, including the following.

  • CREATE_SUSPENDED indicates that the primary thread is in a suspended state and will run only when ResumeThread is called.

  • DETACHED_PROCESS and CREATE_NEW_CONSOLE are mutually exclusive; don't set both. The first flag creates a process without a console, and the second flag gives the new process a console of its own. If neither flag is set, the process inherits the parent's console.

  • CREATE_NEW_PROCESS_GROUP specifies that the new process is the root of a new process group. All processes in a group receive a console control signal (Ctrl-c or Ctrl-break) if they all share the same console. Console control handlers were described in Chapter 4 and illustrated in Program 4-5. These process groups have similarities to UNIX process groups and are described later in this chapter.

Several of the flags control the priority of the new process's threads. The possible values are explained in more detail at the end of Chapter 7. For now, just use the parent's priority (specify nothing) or NORMAL_PRIORITY_CLASS.

lpEnvironment points to an environment block for the new process. If NULL, the process uses the parent's environment. The environment block contains name and value strings, such as the search path.

lpCurDir specifies the drive and directory for the new process. If NULL, the parent's working directory is used.

lpStartupInfo specifies the main window appearance and standard device handles for the new process. Use the parent's information, which is obtained from GetStartupInfo. Alternatively, zero out the associated STARTUPINFO structure before calling CreateProcess. To specify the standard input, output, and error handles, set the standard handler fields (hStdInput, hStdOutput, and hStdError) in the STARTUPINFO structure. For this to be effective, also set another STARTUPINFO member, dwFlags, to STARTF_USESTDHANDLES, and set all the handles that the child process will require. Be certain that the handles are inheritable and that the CreateProcess bInheritHandles flag is set. The Inheritable Handles subsection gives more information and an example.

lpProcInfo specifies the structure for containing the returned process, thread handles, and identification. The PROCESS_INFORMATION structure is as follows:

typedef struct PROCESS_INFORMATION {
   HANDLE hProcess;
   HANDLE hThread;
   DWORD dwProcessId;
   DWORD dwThreadId;

Why do processes and threads need handles in addition to IDs? The ID is unique to the object for its entire lifetime and in all processes, whereas a given process may have several handles, each having distinct attributes, such as security access. For this reason, some process management functions require IDs, and others require handles. Furthermore, process handles are required for the general-purpose, handle-based functions. Examples include the wait functions discussed later in this chapter, which allow waiting on handles for several different object types, including processes. Just as with file handles, process and thread handles should be closed when no longer required.

Note: The new process obtains environment, working directory, and other information from the CreateProcess call. Once this call is complete, any changes in the parent will not be reflected in the child process. For example, the parent might change its working directory after the CreateProcess call, but the child process working directory will not be affected, unless the child changes its own working directory. The two processes are entirely independent.

The UNIX and Windows process models are considerably different. First, Windows has no equivalent to the UNIX fork function, which makes a copy of the parent, including the parent's data space, heap, and stack. fork is difficult to emulate exactly in Windows, and, while this may seem to be a limitation, fork is also difficult to use in a multithreaded UNIX system because there are numerous problems with creating an exact replica of a multithreaded system with exact copies of all threads and synchronization objects, especially on an SMP system. Therefore, fork, by itself, is not really appropriate in any multithreaded system.

CreateProcess is, however, similar to the common UNIX sequence of successive calls to fork and execl (or one of five other exec functions). In contrast to Windows, the search directories in UNIX are determined entirely by the PATH environment variable.

As previously mentioned, Windows does not maintain parent-child relationships among processes. Thus, a child process will continue to run after the creating parent process terminates. Furthermore, there are no process groups in Windows. There is, however, a limited form of process group that specifies all the processes to receive a console control event.

Windows processes are identified both by handles and by process IDs, whereas UNIX has no process handles.

Specifying the Executable Image and the Command Line

Either lpApplicationName or lpCommandLine specifies the executable image name. The rules are as follows.

  • lpApplicationName, if not NULL, is the name of the executable. Quotation marks can be used if the image name contains spaces. More detailed rules are described below.

  • Otherwise, the executable is the first token in lpCommandLine.

Usually, only lpCommandLine is specified, with lpApplicationName being NULL. Nonetheless, there are detailed rules for lpApplicationName.

  • If lpApplicationName is not NULL, it specifies the executable module. Specify the full path and file name, or use a partial name and the current drive and directory will be used; there is no additional searching. Include the file extension, such as .EXE or .BAT, in the name.

  • If the lpApplicationName string is NULL, the first white-space-delimited token in lpCommandLine is the program name. If the name does not contain a full directory path, the search sequence is as follows:

    1. The directory of the current process's image

    2. The current directory

    3. The Windows system directory, which can be retrieved with GetSystemDirectory

    4. The Windows directory, which is retrievable with GetWindowsDirectory

    5. The directories as specified in the environment variable PATH

The new process can obtain the command line using the usual argv mechanism, or it can invoke GetCommandLine to obtain the command line as a single string.

Notice that the command line is not a constant string. This is consistent with the fact that the argv parameters to the main program are not constant. A program could modify its arguments, although it is advisable to make any changes in a copy of the argument string.

The new process is not required to be built with the same UNICODE definition as that of the parent process. All combinations are possible. Using _tmain as discussed in Chapter 2 is helpful in developing code for either UNICODE or ASCII operation.

Inheritable Handles

Frequently, a child process requires access to an object referenced by a handle in the parent; if this handle is inheritable, the child can receive a copy of the parent's open handle. The standard input and output handles are frequently shared with the child in this way. To make a handle inheritable so that a child receives and can use a copy requires several steps.

The bInheritHandles flag on the CreateProcess call determines whether the child process will inherit copies of the inheritable handles of open files, processes, and so on. The flag can be regarded as a master switch applying to all handles.

It is also necessary to make an individual handle inheritable; it is not done by default. To create an inheritable handle, use a SECURITY_ATTRIBUTES structure at creation time or duplicate an existing handle.

The SECURITY_ATTRIBUTES structure has a flag, bInheritHandle, that should be set to TRUE. Also, recall that nLength should be set to sizeof (SECURITY_ATTRIBUTES).

The following code segment shows how an inheritable file or other handle is typically created. In this example, the security descriptor within the security attributes structure is NULL; Chapter 15 shows how to include a security descriptor.

HANDLE h1, h2, h3;
h1 = CreateFile (..., &sa, ... ); /* Inheritable. */
h2 = CreateFile (..., NULL, ... ); /* Not inheritable. */
h3 = CreateFile (..., &sa, ...);
   /* Inheritable. sa can be reused. */

A child process still needs to know the value of an inheritable handle, so the parent needs to communicate handle values to the child using an interprocess communication (IPC) mechanism or by assigning the handle to standard I/O in the STARTUPINFO structure, as is done in the first example of this chapter (Program 6-1) and in several additional examples throughout the book. This is generally the preferred technique because it allows I/O redirection in a standard way and no changes are needed in the child program.

Alternatively, nonfile handles and handles that are not used to redirect standard I/O can be converted to text and placed in a command line or in an environment variable. This approach is valid if the handle is inheritable because both parent and child processes identify the handle with the same handle value. Exercise 6–2 suggests how to demonstrate this, and a solution is presented on the book's Web site.

The inherited handles are distinct copies. Therefore, a parent and child might be accessing the same file using different file pointers. Furthermore, each of the two processes can and should close its own handle.

Figure 6-2 shows how two processes can have distinct handle tables with two distinct handles associated with the same file or other object. Process 1 is the parent, and Process 2 is the child. The handles will have identical values in both processes if the child's handle has been inherited, as is the case with Handles 1 and 3.

06fig02.gifFigure 6-2 Process Handle Tables

On the other hand, the handle values may be distinct. For example, there are two handles for File D, where Process 2 obtained a handle by calling CreateFile rather than by inheritance. Finally, as is the case with Files B and E, one process may have a handle to an object while the other does not. This would be the case when the child process creates the handle or when a handle is duplicated from one process to another, as described in the upcoming Duplicating Handles section.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020