ZwQueryDirectoryFileEx function (ntifs.h)

Article
12/02/2021

The ZwQueryDirectoryFileEx routine returns various information about files in the directory specified by a given file handle.

Syntax

NTSYSAPI NTSTATUS ZwQueryDirectoryFileEx(
  [in]           HANDLE                 FileHandle,
  [in, optional] HANDLE                 Event,
  [in, optional] PIO_APC_ROUTINE        ApcRoutine,
  [in, optional] PVOID                  ApcContext,
  [out]          PIO_STATUS_BLOCK       IoStatusBlock,
  [out]          PVOID                  FileInformation,
  [in]           ULONG                  Length,
  [in]           FILE_INFORMATION_CLASS FileInformationClass,
  [in]           ULONG                  QueryFlags,
  [in, optional] PUNICODE_STRING        FileName
);

Parameters

[in] FileHandle

A handle returned by ZwCreateFile or ZwOpenFile for the file object that represents the directory for which information is being requested. The file object must have been opened for asynchronous I/O if the caller specifies a non-NULL value for Event or ApcRoutine.

[in, optional] Event

An optional handle for a caller-created event. If this parameter is supplied, the caller will be put into a wait state until the requested operation is completed and the given event is set to the Signaled state. This parameter is optional and can be NULL. It must be NULL if the caller will wait for the FileHandle to be set to the Signaled state.

[in, optional] ApcRoutine

An address of an optional, caller-supplied APC routine to be called when the requested operation completes. This parameter is optional and can be NULL. If there is an I/O completion object associated with the file object, this parameter must be NULL.

[in, optional] ApcContext

An optional pointer to a caller-determined context area if the caller supplies an APC or if an I/O completion object is associated with the file object. When the operation completes, this context is passed to the APC, if one was specified, or is included as part of the completion message that the I/O Manager posts to the associated I/O completion object.

This parameter is optional and can be NULL. It must be NULL if ApcRoutine is NULL and there is no I/O completion object associated with the file object.

[out] IoStatusBlock

A pointer to an IO_STATUS_BLOCK structure that receives the final completion status and information about the operation. For successful calls that return data, the number of bytes written to the FileInformation buffer is returned in the structure's Information member.

[out] FileInformation

A pointer to an output buffer that receives the desired information about the file. The structure of the information returned in the buffer is defined by the FileInformationClass parameter.

[in] Length

The size, in bytes, of the buffer pointed to by FileInformation. The caller should set this parameter according to the given FileInformationClass.

[in] FileInformationClass

The type of information to be returned about files in the directory. See the FileInformationClass parameter of NtQueryDirectoryFileEx for the list of possible values.

[in] QueryFlags

One or more of the flags contained in SL_QUERY_DIRECTORY_MASK. See the QueryFlags parameter of NtQueryDirectoryFileEx for the list of possible values.

[in, optional] FileName

An optional pointer to a caller-allocated Unicode string containing the name of a file (or multiple files, if wildcards are used) within the directory specified by FileHandle. This parameter is optional:

If FileName is not NULL, only files whose names match the FileName string are included in the directory scan.
If FileName is NULL:
- If SL_RETURN_SINGLE_ENTRY is not set in QueryFlags, all files are included.
- If SL_RETURN_SINGLE_ENTRY is set, only one file is included.

The FileName is used as a search expression and is captured on the very first call to ZwQueryDirectoryFileEx for a given handle. Subsequent calls to ZwQueryDirectoryFileEx will use the search expression set in the first call. The FileName parameter passed to subsequent calls will be ignored.

Return value

ZwQueryDirectoryFileEx returns STATUS_SUCCESS or an appropriate error status. The set of error status values that can be returned is file system-specific. ZwQueryDirectoryFileEx also returns the number of bytes actually written to the given FileInformation buffer in the Information member of IoStatusBlock. See NtQueryDirectoryFileEx for a list of some possible error codes.

Remarks

ZwQueryDirectoryFileEx returns information about files that are contained in the directory represented by FileHandle.

If provided, FileName determines the entries that are included in the directory scan for all subsequent calls to ZwQueryDirectoryFileEx for a given FileHandle.

If there is at least one matching entry, ZwQueryDirectoryFileEx creates a FILE_XXX_INFORMATION structure for each entry and stores them in the buffer.

Assuming that at least one matching directory entry is found, the number of entries for which information is returned is the smallest of the following:

One entry, if SL_RETURN_SINGLE_ENTRY is set in QueryFlags and FileName is NULL.
The number of entries that match the FileName string, if FileName is not NULL. If the string contains no wildcards, there can be at most one matching entry.
The number of entries whose information fits into the specified buffer.
The number of entries contained in the directory.

On the first call to ZwQueryDirectoryFileEx, if the structure it creates for the first entry found is too large to fit into the output buffer, this routine does the following:

Writes the fixed portion of the structure to FileInformation's output buffer. The fixed portion consists of all fields except the final FileName string. On the first call, but not on subsequent calls, the I/O system ensures that the buffer is large enough to hold the fixed portion of the appropriate FILE_XXX_INFORMATION structure.
Writes to the output buffer as much of the FileName string as will fit.
Returns an appropriate status value such as STATUS_BUFFER_OVERFLOW.

On each call, ZwQueryDirectoryFileEx returns as many FILE_XXX_INFORMATION structures (one per directory entry) as can be contained entirely in the buffer pointed to by FileInformation:

On the first call, ZwQueryDirectoryFileEx returns STATUS_SUCCESS only if the output buffer contains at least one complete structure.
On subsequent calls, if the output buffer contains no structures, ZwQueryDirectoryFileEx returns STATUS_SUCCESS but sets IoStatusBlock->Information = 0 to notify the caller of this condition. In this case, the caller should allocate a larger buffer and call ZwQueryDirectoryFileEx again. No information about any remaining entries is reported. Thus, except in the cases listed above where only one entry is returned, ZwQueryDirectoryFileEx must be called at least twice to enumerate the contents of an entire directory.

When calling ZwQueryDirectoryFileEx, you might see changes made to the directory that occur in parallel with ZwQueryDirectoryFileEx calls. This behavior is dependent on the implementation of the underlying file system.

The final call to ZwQueryDirectoryFileEx returns an empty output buffer and reports an appropriate status value such as STATUS_NO_MORE_FILES.

If ZwQueryDirectoryFileEx is called multiple times on the same directory and some other operation changes the contents of that directory, any changes might or might not be seen, depending on the timing of the operations.

ZwQueryDirectoryFileEx returns zero in any member of a FILE_XXX_INFORMATION structure that is not supported by the file system.

Callers of ZwQueryDirectoryFileEx must be running at IRQL = PASSIVE_LEVEL and with special kernel APCs enabled.

For information about other file information query routines, see File Objects.

Note

If the call to the ZwQueryDirectoryFileEx function occurs in user mode, you should use the name "NtQueryDirectoryFileEx" instead of "ZwQueryDirectoryFileEx".

For calls from kernel-mode drivers, the NtXxx and ZwXxx versions of a Windows Native System Services routine can behave differently in the way that they handle and interpret input parameters. For more information about the relationship between the NtXxx and ZwXxx versions of a routine, see Using Nt and Zw Versions of the Native System Services Routines.

Requirements

Requirement	Value
Minimum supported client	Windows 10, version 1709
Header	ntifs.h
IRQL	PASSIVE_LEVEL (see Remarks section)