Tcl Built-In Commands                                    tell(1T)





NAME
     tell - Return current access position for an open channel

SYNOPSIS
     tell channelId



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  particu-  
     lar  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(1T),   open(1T),   close(1T),    gets(1T),    seek(1T),
     TclStandardChannels(3TCL)


KEYWORDS
     access position, channel, seeking

ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:






Tcl                     Last change: 8.1                        1






Tcl Built-In Commands                                    tell(1T)



     
       ATRIBUTE TYPE     ATRIBUTE VALUE
    
     Availability         SUNWTcl        
    
     Interface Stability  Uncommitted    
    

NOTES
     Source for Tcl is available on http:/opensolaris.org.













































Tcl                     Last change: 8.1                        2