|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 command flushes all buffered output for the channel before the command returns, even if the channel is in nonblocking 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.
Read a file twice:set f [open file.txt] set data1 [read $f] seek $f 0 set data2 [read $f] close $f # $data1 == $data2 if the file wasnt 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
file(n), open(n), close(n), gets(n), tell(n), Tcl_StandardChannels(3)
access position, file, seek