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

______________________________________________________________________________

NAME
       tell - Return current access position for an open channel

SYNOPSIS
       tell channelId
_________________________________________________________________

DESCRIPTION
       Returns	an  integer string giving the current access position in chan‐
       nelId.  This value returned is a byte offset that can be passed to seek
       in  order  to set the channel to a particular position.	Note that this
       value is in terms of  bytes,  not  characters  like  read.   The	 value
       returned is -1 for channels that do not support seeking.

       ChannelId must be an identifier for an open channel such as a Tcl stan‐
       dard channel (stdin, stdout, or stderr), the return value from an invo‐
       cation  of  open or socket, or the result of a channel creation command
       provided by a Tcl extension.

EXAMPLE
       Read a line from a file channel only if it starts with foobar:

	      # Save the offset in case we need to undo the read...
	      set offset [tell $chan]
	      if {[read $chan 6] eq "foobar"} {
		  gets $chan line
	      } else {
		  set line {}
		  # Undo the read...
		  seek $chan $offset
	      }

SEE ALSO
       file(n), open(n), close(n), gets(n), seek(n), Tcl_StandardChannels(3)

KEYWORDS
       access position, channel, seeking

Tcl				      8.1			       tell(n)

                             _         _         _ 
                            | |       | |       | |     
                            | |       | |       | |     
                         __ | | __ __ | | __ __ | | __  
                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 

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