seek(n) Tcl Built-In Commands seek(n)
seek - Change the access position for an open channel
seek channelId offset ?origin?
Changes the current access position for channelId. ChannelId must be a
channel identifier such as returned from a previous invocation of open
or socket. 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 fol-
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 nonblocking mode. It also dis-
cards 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.
file(n), open(n), close(n), gets(n), tell(n)
access position, file, seek
Tcl 8.1 seek(n)