52 lines
2.7 KiB
HTML
52 lines
2.7 KiB
HTML
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<HTML><HEAD><TITLE>Tcl Built-In Commands - seek manual page</TITLE></HEAD><BODY>
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<H3><A NAME="M2">NAME</A></H3>
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seek - Change the access position for an open channel
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<H3><A NAME="M3">SYNOPSIS</A></H3>
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<B>seek </B><I>channelId offset </I>?<I>origin</I>?<BR>
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<H3><A NAME="M4">DESCRIPTION</A></H3>
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Changes the current access position for <I>channelId</I>.
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<I>ChannelId</I> must be a channel identifier such as returned from a
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previous invocation of <B><A HREF="../TkCmd/open.htm">open</A></B> or <B><A HREF="../TkCmd/socket.htm">socket</A></B>.
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The <I>offset</I> and <I>origin</I>
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arguments specify the position at which the next read or write will occur
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for <I>channelId</I>. <I>Offset</I> must be an integer (which may be
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negative) and <I>origin</I> must be one of the following:
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<P>
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<DL>
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<P><DT><A NAME="M5"><B>start</B></A><DD>
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The new access position will be <I>offset</I> bytes from the start
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of the underlying file or device.
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<P><DT><A NAME="M6"><B>current</B></A><DD>
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The new access position will be <I>offset</I> bytes from the current
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access position; a negative <I>offset</I> moves the access position
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backwards in the underlying file or device.
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<P><DT><A NAME="M7"><B>end</B></A><DD>
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The new access position will be <I>offset</I> bytes from the end of
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the file or device. A negative <I>offset</I> places the access position
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before the end of file, and a positive <I>offset</I> places the access
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position after the end of file.
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<P></DL>
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<P>
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The <I>origin</I> argument defaults to <B>start</B>.
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<P>
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The command flushes all buffered output for the channel before the command
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returns, even if the channel is in nonblocking mode.
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It also discards any buffered and unread input.
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This command returns an empty string.
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An error occurs if this command is applied to channels whose underlying
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file or device does not support seeking.
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<P>
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Note that <I>offset</I> values are byte offsets, not character
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offsets. Both <B>seek</B> and <B><A HREF="../TkCmd/tell.htm">tell</A></B> operate in terms of bytes,
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not characters, unlike <B><A HREF="../TkCmd/read.htm">read</A></B>.
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<H3><A NAME="M8">SEE ALSO</A></H3>
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<B><A HREF="../TkCmd/file.htm">file</A></B>, <B><A HREF="../TkCmd/open.htm">open</A></B>, <B><A HREF="../TkCmd/close.htm">close</A></B>, <B><A HREF="../TkCmd/gets.htm">gets</A></B>, <B><A HREF="../TkCmd/tell.htm">tell</A></B>
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<H3><A NAME="M9">KEYWORDS</A></H3>
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<A href="../Keywords/A.htm#access position">access position</A>, <A href="../Keywords/F.htm#file">file</A>, <A href="../Keywords/S.htm#seek">seek</A>
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<HR><PRE>
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<A HREF="../copyright.htm">Copyright</A> © 1993 The Regents of the University of California.
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<A HREF="../copyright.htm">Copyright</A> © 1994-1996 Sun Microsystems, Inc.
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<A HREF="../copyright.htm">Copyright</A> © 1995-1997 Roger E. Critchlow Jr.</PRE>
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</BODY></HTML>
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