NAME

       tell - Return current access position for an open channel

SYNOPSIS

       tell channelId
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DESCRIPTION

       Returns an integer string giving the current access position in channelId.  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 standard channel (stdin, stdout, or
       stderr), the return value from an invocation 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(3tcl), open(3tcl), close(3tcl), gets(3tcl), seek(3tcl), Tcl_StandardChannels(3tcl)

KEYWORDS

       access position, channel, seeking

Tcl                                                    8.1                                            tell(3tcl)