tcl7.6 User Commands - seek






NAME

     seek - Change the access position for an open channel


SYNOPSIS

     seek channelId offset ?origin?





DESCRIPTION

     Changes the current access position  for  channelId.   Chan-
     nelId  must  be a channel identifier such as returned from a
     previous invocation of open or socket.  The offset and  ori-
     gin 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  under-
               lying 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  command returns, even if the channel is in non-
     blocking mode.  It also discards  any  buffered  and  unread
     input.   This  command  returns  an  empty string.  An error
     occurs if this command is applied to channels whose underly-
     ing file or device does not support seeking.



KEYWORDS

     access position, file, seek