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seek(3tcl) | Tcl Built-In Commands | seek(3tcl) |
NAME¶
seek - Change the access position for an open channelSYNOPSIS¶
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 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. 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.
EXAMPLES¶
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 wasn't updated
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
SEE ALSO¶
file(3tcl), open(3tcl), close(3tcl), gets(3tcl), tell(3tcl), Tcl_StandardChannels(3tcl)KEYWORDS¶
access position, file, seek8.1 | Tcl |