Tcl Built-In Commands tell(1T)
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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 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),Tcl_StandardChannels(3TCL)
KEYWORDS access position, channel, seekingATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes: Tcl Last change: 8.1 1Tcl Built-In Commands tell(1T)
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| ATTRIBUTE TYPE | ATTRIBUTE VALUE|
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| Availability | runtime/tcl-8 |
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| Interface Stability| Uncommitted ||____________________|_________________|
NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.1 2