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Seek.md

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NAME

Seek -- Set the current position for reading and writing

SYNOPSIS

    oldPosition = Seek( file, position, mode )
    D0                  D1    D2        D3

    LONG Seek(BPTR, LONG, LONG)

FUNCTION

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. 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.

INPUTS

file - BCPL pointer to a file handle position - integer mode - integer

RESULTS

oldPosition - integer

BUGS The V36 and V37 ROM filesystem (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.

SEE ALSO

Read, Write, SetFileSize