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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

High-Level File Access Routines / Reading, Writing, and Closing Files

FSWrite

You can use the FSWrite function to write any number of bytes to an open file.

FUNCTION FSWrite (refNum: Integer; VAR count: LongInt; 
                  buffPtr: Ptr): OSErr;

refNum

The file reference number of an open file.

count

On input, the number of bytes to write to the file; on output, the number of bytes actually written.

buffPtr

A pointer to the data buffer from which the bytes are to be written.

DESCRIPTION

The FSWrite function takes the specified number of bytes from the specified data buffer and attempts to write them to the specified file. Because the write operation begins at
the current mark, you might want to set the mark first by calling the SetFPos function.

If the write operation completes successfully, FSWrite moves the file mark to the
byte following the last byte written and returns noErr. If you try to write past the
logical end-of-file, FSWrite moves the logical end-of-file. If you try to write past
the physical end-of-file, FSWrite adds one or more clumps to the file and moves the physical end-of-file accordingly.

Note

The low-level PBWrite function lets you set the mark without having to call SetFPos.

RESULT CODES

noErr	0	No error
dskFulErr	-34	Disk full
ioErr	-36	I/O error
fnOpnErr	-38	File not open
posErr	-40	Attempt to position mark before start of file
wPrErr	-44	Hardware volume lock
fLckdErr	-45	File is locked
vLckdErr	-46	Software volume lock
paramErr	-50	Negative count
rfNumErr	-51	Bad reference number
wrPermErr	-61	Read/write permission doesn't allow writing