Seek

Set the current position for reading and writing

Seek() sets the read/write cursor for the file 'file' to the position 'position'. This position is used by both Read() and Write() as a place to start reading or writing, respectively. The result is the current absolute position in the file, or -1 if an error occurs, in which case IoErr() can be used to find more information. 'mode' can be OFFSET_BEGINNING, OFFSET_CURRENT or OFFSET_END. It is used to specify the relative start position. For example, 20 from current is a position 20 bytes forward from current, -20 is 20 bytes back from current.

So that to find out where you are, seek zero from current. The end of the file is a Seek() positioned by zero from end. You cannot Seek() beyond the end of a file.

file

BCPL pointer to a FileHandle

position

integer

mode

integer

oldPosition

integer. -1 indicates failure; call IoErr() to find out why Seek() failed.

Amiga file system operations limit the size of files to 2 GBytes (2,147,483,647 bytes). It is safe to assume that random access to files which do not exceed this limitation is reliable, unless the file system itself imposes additional size limitations. File systems may even make larger files accessible, but you may find that random access becomes unreliable. Writing/reading data sequentially beyond the 2 GByte limit may become unreliable, too.

Random access through Seek() is a file system feature, i.e. named files need not be read or written sequentially. Handlers such as SER: or PRT: have no concept of a file "size" and can be written or read (if possible) sequentially only. They will return failure for an attempt to use Seek() and indicate through IoErr() why the Seek() operation was denied.

The Seek() function combines the features of the 'C' programming language runtime library functions fseek() and ftell().

The V36 and V37 ROM file system (and V36/V37 l:fastfilesystem) returns the current position instead of -1 on an error. It sets IoErr() to 0 on success, and an error code on an error. This bug was fixed in the V39 file system.

Read(), Write(), SetFileSize()