Chapter 7 File Manager Functions

typedef struct {
int32	size;	/* size in bytes of a kuhvkjhgvku
		volume */
int32	used;	/* number of bytes used on volume
		*/
int32	free;	/* number of bytes available for
		use on volume */
}	VInfoRec;

File Manager Functions

Performing Basic File Operations

FCreate

syntax	MgErr	FCreate(fdp, path, permissions, openMode,
		denyMode, group);

FCreate creates a file with the name and location specified by path and with the specified permissions, and opens it for writing and reading, as specified by openMode. If the file already exists, an error is returned.

You can use denyMode to control concurrent access to the file from within LabVIEW. The group parameter allows you to assign the file to a UNIX group; under Windows or Macintosh, group is ignored.

If the function creates the file, the resulting file descriptor is stored in the address referred to by fdp. If an error occurs, the function stores 0 in the address referred to by fdp and returns an error.

Note:	Before attempting to call this function, make sure that you understand
	how to use the fdp parameter. See the Pointers as Parameters section of
	Chapter 1, CIN Overview, for more information about this parameter.
Parameter	Type	Description
fdp	File *	Address at which FCreate stores the file
		descriptor for the new file. If FCreate fails, it
		stores 0 in the address fdp.
		See the Pointers as Parameters section of
		Chapter 1, CIN Overview, for more information
		about using this parameter.
path	Path	Path of the file that you want to create.

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	permissions	int32	Permissions to assign to the new file. See the File
			Manager Data Structures section for a description
			of permissions.
	openMode	int32	Access mode to use in opening the file. Can have the
			following values, which are defined in the file
			extcode.h.
			• openReadOnly: Open for reading.
			• openWriteOnly: Open for writing
			• openReadWrite: Open for both reading
			and writing
	denyMode	int32	Mode that determines what level of concurrent
			access to the file is allowed. Can have the following
			values, which are defined in the file extcode.h.
			• denyReadWrite: Prevents others from
			reading from and writing to the file while it is
			open.
			• denyWriteOnly: Prevents others from
			writing to the file only while it is open
			• denyNeither: allows others to read from
			and write to the file while it is open.
	group	PStr	UNIX group you want to assign to the new file.
returns		MgErr, which can contain the errors in the following list.
	Error	Description
	mgArgErr	A bad argument was passed to the function. Verify path.
	fIsOpen	File is already open for writing. This error is returned only on the
		Macintosh and the Sun. The PC returns fIOErr when the file is
		already open for writing.
	fNoPerm	Access denied (something is locked/protected).
	fDupPath	A file of that name already exists.
	fTMFOpen	Too many files open.
	fIOErr	Unspecified I/O error occurred.

FCreateAlways

syntax	MgErr	FCreateAlways(fdp, path, permissions,
		openMode, denyMode, group);

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FCreateAlways creates a file with the name and location specified by path and with the specified permissions, and opens the file for writing and reading, as specified by openMode. If the file already exists, this function opens and truncates the file.

You can use denyMode to control concurrent access to the file from within LabVIEW. The group parameter allows you to assign the file to a UNIX group; under Windows or Macintosh, group is ignored.

If the function creates the file, the resulting file descriptor is stored in the address referred to by fdp. If an error occurs, the function stores 0 in the address referred to by fdp and returns an error.

Note: Before attempting to call this function, make sure that you understand how to use the fdp parameter. See the Pointers as Parameters section of Chapter 1, CIN Overview, for more information about this parameter.

Parameter	Type	Description
fdp	File *	Address at which FCreateAlways stores the file
		descriptor for the new file. If FCreateAlways
		fails, it stores 0 in the address fdp.
		See the Pointers as Parameters section of
		Chapter 1, CIN Overview, for more information
		about using this parameter.
path	Path	Path of the file that you want to create.
permissions	int32	Permissions to assign to the new file. See the File
		Manager Data Structures section of this chapter for
		a description of permissions.
openMode	int32	See FMOpen for a description of openMode.
denyMode	int32	See FMOpen for a description of denyMode.
group	PStr	UNIX group you want to assign to the new file.
returns	MgErr, which can contain the errors in the following list.
Error	Description
mgArgErr	A bad argument was passed to the function. Verify path.
fIsOpen	File is already open for writing. This error is returned only on the
	Macintosh and the Sun. The PC returns fIOErr when the file is
	already open for writing.
fNoPerm	Access denied (something is locked/protected).
fDupPath	A file of that name exists.
fTMFOpen	Too many files open.
fIOErr	Unspecified I/O error occurred.

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Chapter 7 File Manager Functions

FMClose

syntax

MgErr

FMClose(fd);

FMClose closes the file associated with the file descriptor fd.

Parameter	Type	Description
fd	File	File descriptor associated with the file you want to
		close.

returns		MgErr, which can contain the errors in the following list.
	Error	Description
	mgArgErr	Not a valid file descriptor.
	fIOErr	Unspecified I/O error occurred.

FMOpen

syntax	MgErr	FMOpen(fdp, path, openMode, denyMode);
Note:	Before attempting to call this function, make sure that you understand
	how to use the fdp parameter. See the Pointers as Parameters section of
	Chapter 1, CIN Overview, for more information about this parameter.

FMOpen opens a file with the name and location specified by path for writing and reading, as specified by openMode.

With the denyMode parameter, you control concurrent access to the file from within LabVIEW.

If this function opens the file, the resulting file descriptor is stored in the address referred to by fdp. If an error occurs, 0 is stored in the address referred to by fdp and the error is returned.

Parameter	Type	Description
fdp	File *	Address at which FMOpen stores the file descriptor
		for the opened file. If the function fails, FMOpen
		stores 0 in the address fdp.

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		See the Pointers as Parameters section of
		Chapter 1, CIN Overview, for more information
		about using this parameter.
path	Path	Path of the file that you want to open.
openMode	int32	Access mode to use in opening the file. Can have the
		following values, which are defined in the file
		extcode.h.
		• openReadOnly: Open for reading.
		• openWriteOnly: Open for writing; file is
		not truncated (data is not removed). On the
		Macintosh, this mode provides true write-
		only access to files. On a PC or a UNIX
		system, LabVIEW I/O functions are built in
		the C standard I/O library, with which you
		have write-only access to a file only if you are
		truncating the file or making the access
		append-only. Therefore, this mode actually
		allows both read and write access to files on
		a PC or UNIX system.
		• openReadWrite: Open for both reading
		and writing.
		• openWriteOnlyTruncate: Open for
		writing; truncates the file.
denyMode	int32	Mode that determines what level of concurrent
		access to the file is allowed. Can have the following
		values, which are defined in the file extcode.h.
		• denyReadWrite: Prevents others from
		reading from and writing to the file while it is
		open.
		• denyWriteOnly: Prevents others from
		writing to the file only while it is open
		• denyNeither: allows others to read from
		and write to the file while it is open.
returns	MgErr, which can contain the errors in the following list.
Error	Description
mgArgErr	A bad argument was passed to the function. Verify path.

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