GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  -  SEEK (n)

NAME

seek - Change the access position for an open channel

CONTENTS

Synopsis
Description
Examples
Keywords

SYNOPSIS

seek channelId offset ?origin?

   








\L’|0u-1v’\l’75u+3n_’\L’0u+1v-0u’\l’|0u-1.5n_’



\L’|0u-1v’\L’0u+1v-0u’\l’|0u-1.5n_’





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.
The origin argument defaults to start.

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.

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


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


SEE ALSO

file(n), open(n), close(n), gets(n), tell(n), Tcl_StandardChannels(3)

KEYWORDS

access position, file, seek
Search for    or go to Top of page |  Section n |  Main Index


Tcl SEEK (n) 8.1

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.