seek

seek(n)                      Tcl Built-In Commands                     seek(n)



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NAME
       seek - Change the access position for an open channel

SYNOPSIS
       seek channelId offset ?origin?
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DESCRIPTION
       Changes the current access position for channelId.  ChannelId must be a
       channel identifier such as returned from a previous invocation of  open
       or  socket.   The  offset  and origin arguments specify the position at
       which the next read or write will occur for channelId. Offset  must  be
       an  integer  (which may be negative) and origin must be one of the fol-
       lowing:

       start     The new access position will be offset bytes from  the  start
                 of the underlying file or device.

       current   The new access position will be offset bytes from the current
                 access position; a negative offset moves the access  position
                 backwards in the underlying file or device.

       end       The  new access position will be offset bytes from the end of
                 the file or device.  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.

       The origin argument defaults to start.

       The command flushes all buffered output for the channel before the com-
       mand returns, even if the channel is in nonblocking mode.  It also dis-
       cards any buffered and unread input.  This  command  returns  an  empty
       string.   An  error occurs if this command is applied to channels whose
       underlying file or device does not support seeking.

       Note that offset values are byte offsets, not character offsets.   Both |
       seek and tell operate in terms of bytes, not characters, unlike read.


SEE ALSO
       file(n), open(n), close(n), gets(n), tell(n)


KEYWORDS
       access position, file, seek



Tcl                                   8.1                              seek(n)