seek - Change the access position for an open channel
seek channelId offset ?origin?
seek(1t) Tcl Built-In Commands seek(1t) ______________________________________________________________________________ NAME seek - Change the access position for an open channel SYNOPSIS seek channelId offset ?origin? ______________________________________________________________________________ DESCRIPTION Changes the current access position for channelId. 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. The offset and origin arguments specify the position at which the next read or write will occur for channelId. Offset must be an integer (which may be negative) and origin must be one of the following: start The new access position will be offset bytes from the start of the underlying file or device. current The new access position will be offset bytes from the current access position; a negative offset moves the access position backwards in the underlying file or device. end The new access position will be offset bytes from the end of the file or device. A negative offset places the access position before the end of file, and a positive offset places the access position after the end of file. The origin argument defaults to start. The command flushes all buffered output for the channel before the com- mand returns, even if the channel is in non-blocking mode. It also discards any buffered and unread input. This command returns an empty string. An error occurs if this command is applied to channels whose underlying file or device does not support seeking. Note that offset values are byte offsets, not character offsets. Both seek and tell operate in terms of bytes, not characters, unlike read. EXAMPLES Read a file twice: set f [open file.txt] set data1 [read $f] seek $f 0 set data2 [read $f] close $f # $data1 eq $data2 if the file wasn't updated Read the last 10 bytes from a file: set f [open file.data] # This is guaranteed to work with binary data but # may fail with other encodings... fconfigure $f -translation binary seek $f -10 end set data [read $f 10] close $f 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), tell(n), Tcl_StandardChannels(3) KEYWORDS access position, file, seek 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 seek(1t)