tell - Return current access position for an open channel
tell channelId
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
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
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)