Chapter 7 File Manager Functions
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.
fNotFound	File not found.
fTMFOpen	Too many files open.
fIOErr	Unspecified I/O error occurred.

FMRead

syntax MgErr FMRead(fd, inCount, outCountp, buffer);

FMRead reads inCount bytes from the file specified by the file descriptor fd. The function starts from the current position mark (see the FSeek and FTell functions), and reads the data into memory, starting at the address specified by buffer.

The function stores the actual number of bytes read in *outCountp. The number of bytes can be less than inCount if the function encounters end-of-file before reading inCount bytes. The number of bytes will be zero if any other error occurs.

	Parameter	Type	Description
	fd	File	File descriptor associated with the file from which
			you want to read.
	inCount	int32	Number of bytes you want to read.
	outCountp	int32 *	Address at which FMRead stores the number of
			bytes read. FMRead will not store any value if
			NULL is passed.
			See the Pointers as Parameters section of
			Chapter 1, CIN Overview, for more information
			about using this parameter.
	buffer	UPtr	Address where FMRead will store the data.
returns		MgErr, which can contain the errors in the following list.
	Error	Description
	mgArgErr	Not a valid file descriptor or inCount < 0.
	fEOF	EOF encountered.
	fIOErr	Unspecified I/O error occurred.

FMWrite

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LabVIEW Code Interface Reference Manual