MsiEnumClientsExA function (msi.h)

Article
02/09/2023

The MsiEnumClientsEx function enumerates the installed applications that use a specified component. The function retrieves a product code for an application each time it is called.

Windows Installer 4.5 or earlier: Not supported. This function is available beginning with Windows Installer 5.0.

Syntax

UINT MsiEnumClientsExA(
  [in]                LPCSTR            szComponent,
  [in, optional]      LPCSTR            szUserSid,
  [in]                DWORD             dwContext,
  [in]                DWORD             dwProductIndex,
  [out, optional]     CHAR [39]         szProductBuf,
  [out, optional]     MSIINSTALLCONTEXT *pdwInstalledContext,
  [out, optional]     LPSTR             szSid,
  [in, out, optional] LPDWORD           pcchSid
);

Parameters

[in] szComponent

The component code GUID that identifies the component. The function enumerates the applications that use this component.

[in, optional] szUserSid

A null-terminated string value that contains a security identifier (SID.) The enumeration of applications extends to users identified by this SID. The special SID string s-1-1-0 (Everyone) enumerates all applications for all users in the system. A SID value other than s-1-1-0 specifies a user SID for a particular user and enumerates the instances of applications installed by the specified user.

SID type	Meaning
NULL	Specifies the currently logged-on user.
User SID	Specifies an enumeration for a particular user. An example of an user SID is "S-1-3-64-2415071341-1358098788-3127455600-2561".
s-1-1-0	Specifies an enumeration for all users in the system.

Note The special SID string s-1-5-18 (System) cannot be used to enumerate applications that exist in the per-machine installation context. Setting the SID value to s-1-5-18 returns ERROR_INVALID_PARAMETER. When dwContext is set to MSIINSTALLCONTEXT_MACHINE only, the value of szUserSid must be NULL.

[in] dwContext

A flag that extends the enumeration to instances of applications installed in the specified installation context. The enumeration includes only instances of applications that are installed by the users identified by szUserSid.

This can be a combination of the following values.

Context	Meaning
MSIINSTALLCONTEXT_USERMANAGED 1	Include applications installed in the per–user–managed installation context.
MSIINSTALLCONTEXT_USERUNMANAGED 2	Include applications installed in the per–user–unmanaged installation context.
MSIINSTALLCONTEXT_MACHINE 4	Include applications installed in the per-machine installation context. When dwInstallContext is set to MSIINSTALLCONTEXT_MACHINE only, the value of the szUserSID parameter must be NULL.

[in] dwProductIndex

Specifies the index of the application to retrieve. The value of this parameter must be zero (0) in the first call to the function. For each subsequent call, the index must be incremented by 1. The index should only be incremented if the previous call to the function returns ERROR_SUCCESS.

[out, optional] szProductBuf

A string value that receives the product code for the application. The length of the buffer at this location should be large enough to hold a null-terminated string value containing the product code. The first 38 TCHAR characters receives the GUID for the component, and the 39th character receives a terminating NULL character.

[out, optional] pdwInstalledContext

A flag that gives the installation context of the application.

This can be a combination of the following values.

Context	Meaning
MSIINSTALLCONTEXT_USERMANAGED 1	The application is installed in the per–user–managed installation context.
MSIINSTALLCONTEXT_USERUNMANAGED 2	The application is installed in the per–user–unmanaged installation context.
MSIINSTALLCONTEXT_MACHINE 4	The application is in the per-machine installation installation context.

[out, optional] szSid

Receives the security identifier (SID) that identifies the user that installed the application. The location receives an empty string value if this instance of the application exists in a per-machine installation context.

The length of the buffer should be large enough to hold a null-terminated string value containing the SID. If the buffer is too small, the function returns ERROR_MORE_DATA and the location pointed to by pcchSid receives the number of TCHAR in the SID, not including the terminating NULL character.

If szSid is set to NULL and pcchSid is a valid pointer to a location in memory, the function returns ERROR_SUCCESS and the location receives the number of TCHAR in the SID, not including the terminating null character. The function can then be called again to retrieve the value, with the szSid buffer resized large enough to contain *pcchSid + 1 characters.

SID type	Meaning
Empty string	The application is installed in a per-machine installation context.
User SID	The SID for the user that installed the product.

[in, out, optional] pcchSid

Pointer to a location in memory that contains a variable that specifies the number of TCHAR in the SID, not including the terminating null character. When the function returns, this variable is set to the size of the requested SID whether or not the function can successfully copy the SID and terminating null character into the buffer location pointed to by szSid. The size is returned as the number of TCHAR in the requested value, not including the terminating null character.

This parameter can be set to NULL only if szSid is also NULL, otherwise the function returns ERROR_INVALID_PARAMETER. If szSid and pcchSid are both set to NULL, the function returns ERROR_SUCCESS if the SID exists, without retrieving the SID value.

Return value

The MsiEnumClientsEx function returns one of the following values.

Return code	Description
ERROR_ACCESS_DENIED	Administratator privileges are required to enumerate components of applications installed by users other than the current user.
ERROR_BAD_CONFIGURATION	The configuration data is corrupt.
ERROR_INVALID_PARAMETER	An invalid parameter is passed to the function.
ERROR_NO_MORE_ITEMS	There are no more applications to enumerate.
ERROR_SUCCESS	The function succeeded.
ERROR_MORE_DATA	The provided buffer was too small to hold the entire value.
ERROR_FUNCTION_FAILED	The function failed.

Remarks

Note

The msi.h header defines MsiEnumClientsEx as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows Installer 5.0 on Windows Server 2012, Windows 8, Windows Server 2008 R2 or Windows 7. See the Windows Installer Run-Time Requirements for information about the minimum Windows service pack that is required by a Windows Installer version.
Target Platform	Windows
Header	msi.h
Library	Msi.lib
DLL	Msi.dll

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