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man pages section 1: User Commands

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Updated: Thursday, March 14, 2019
 
 

tell (1t)

Name

tell - Return current access position for an open channel

Synopsis

tell channelId

Description

tell(1t)                     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 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
              }


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | runtime/tcl-8    |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+
SEE ALSO
       file(n), open(n), close(n), gets(n), seek(n), Tcl_StandardChannels(3)

KEYWORDS
       access position, channel, seeking



NOTES
       This    software    was    built    from    source     available     at
       https://github.com/oracle/solaris-userland.    The  original  community
       source was downloaded from  http://prdownloads.sourceforge.net/tcl/tcl-
       core8.6.7-src.tar.gz

       Further information about this software can be found on the open source
       community website at https://www.tcl.tk/.



Tcl                                   8.1                             tell(1t)