change the access position for an open file
seekfileId offset [origin]
Changes the current access position for fileId.
fileId must have been the return
value from a previous call to open, or it may be stdin,
stdout, or stderr to refer to one of the standard
The offset and origin arguments specify the position at
which the next read or write will occur for fileId.
offset must be an integer (which may be negative) and origin
must be one of the following:
The new access position will be offset bytes from the start
of the file.
The new access position will be offset bytes from the current
access position; a negative offset moves the access position
backwards in the file.
The new access position will be offset bytes from the end of
the file. A negative offset places the access position before
the end-of-file, and a positive offset places the access position
after the end-of-file.