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115 lines
6.3 KiB
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<HTML><HEAD><TITLE>Tcl Built-In Commands - after manual page</TITLE></HEAD><BODY>
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<DL>
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<DD><A HREF="after.htm#M2" NAME="L19">NAME</A>
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<DL><DD>after - Execute a command after a time delay</DL>
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<DD><A HREF="after.htm#M3" NAME="L20">SYNOPSIS</A>
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<DL>
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<DD><B>after </B><I>ms</I>
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<DD><B>after </B><I>ms </I>?<I>script script script ...</I>?
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<DD><B>after cancel </B><I>id</I>
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<DD><B>after cancel </B><I>script script script ...</I>
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<DD><B>after idle </B>?<I>script script script ...</I>?
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<DD><B>after info </B>?<I>id</I>?
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</DL>
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<DD><A HREF="after.htm#M4" NAME="L21">DESCRIPTION</A>
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<DL>
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<DD><A HREF="after.htm#M5" NAME="L22"><B>after </B><I>ms</I></A>
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<DD><A HREF="after.htm#M6" NAME="L23"><B>after </B><I>ms </I>?<I>script script script ...</I>?</A>
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<DD><A HREF="after.htm#M7" NAME="L24"><B>after cancel </B><I>id</I></A>
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<DD><A HREF="after.htm#M8" NAME="L25"><B>after cancel </B><I>script script ...</I></A>
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<DD><A HREF="after.htm#M9" NAME="L26"><B>after idle </B><I>script </I>?<I>script script ...</I>?</A>
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<DD><A HREF="after.htm#M10" NAME="L27"><B>after info </B>?<I>id</I>?</A>
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</DL>
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<DD><A HREF="after.htm#M11" NAME="L28">SEE ALSO</A>
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<DD><A HREF="after.htm#M12" NAME="L29">KEYWORDS</A>
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</DL><HR>
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<H3><A NAME="M2">NAME</A></H3>
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after - Execute a command after a time delay
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<H3><A NAME="M3">SYNOPSIS</A></H3>
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<B>after </B><I>ms</I><BR>
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<B>after </B><I>ms </I>?<I>script script script ...</I>?<BR>
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<B>after cancel </B><I>id</I><BR>
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<B>after cancel </B><I>script script script ...</I><BR>
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<B>after idle </B>?<I>script script script ...</I>?<BR>
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<B>after info </B>?<I>id</I>?<BR>
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<H3><A NAME="M4">DESCRIPTION</A></H3>
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This command is used to delay execution of the program or to execute
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a command in background sometime in the future. It has several forms,
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depending on the first argument to the command:
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<P>
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<DL>
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<P><DT><A NAME="M5"><B>after </B><I>ms</I></A><DD>
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<I>Ms</I> must be an integer giving a time in milliseconds.
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The command sleeps for <I>ms</I> milliseconds and then returns.
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While the command is sleeping the application does not respond to
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events.
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<P><DT><A NAME="M6"><B>after </B><I>ms </I>?<I>script script script ...</I>?</A><DD>
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In this form the command returns immediately, but it arranges
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for a Tcl command to be executed <I>ms</I> milliseconds later as an
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event handler.
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The command will be executed exactly once, at the given time.
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The delayed command is formed by concatenating all the <I>script</I>
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arguments in the same fashion as the <B><A HREF="../TkCmd/concat.htm">concat</A></B> command.
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The command will be executed at global level (outside the context
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of any Tcl procedure).
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If an error occurs while executing the delayed command then the
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<B><A HREF="../TkCmd/bgerror.htm">bgerror</A></B> mechanism is used to report the error.
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The <B>after</B> command returns an identifier that can be used
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to cancel the delayed command using <B>after cancel</B>.
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<P><DT><A NAME="M7"><B>after cancel </B><I>id</I></A><DD>
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Cancels the execution of a delayed command that
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was previously scheduled.
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<I>Id</I> indicates which command should be canceled; it must have
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been the return value from a previous <B>after</B> command.
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If the command given by <I>id</I> has already been executed then
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the <B>after cancel</B> command has no effect.
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<P><DT><A NAME="M8"><B>after cancel </B><I>script script ...</I></A><DD>
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This command also cancels the execution of a delayed command.
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The <I>script</I> arguments are concatenated together with space
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separators (just as in the <B><A HREF="../TkCmd/concat.htm">concat</A></B> command).
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If there is a pending command that matches the string, it is
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cancelled and will never be executed; if no such command is
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currently pending then the <B>after cancel</B> command has no effect.
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<P><DT><A NAME="M9"><B>after idle </B><I>script </I>?<I>script script ...</I>?</A><DD>
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Concatenates the <I>script</I> arguments together with space
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separators (just as in the <B><A HREF="../TkCmd/concat.htm">concat</A></B> command), and arranges
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for the resulting script to be evaluated later as an idle callback.
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The script will be run exactly once, the next time the event
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loop is entered and there are no events to process.
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The command returns an identifier that can be used
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to cancel the delayed command using <B>after cancel</B>.
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If an error occurs while executing the script then the
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<B><A HREF="../TkCmd/bgerror.htm">bgerror</A></B> mechanism is used to report the error.
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<P><DT><A NAME="M10"><B>after info </B>?<I>id</I>?</A><DD>
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This command returns information about existing event handlers.
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If no <I>id</I> argument is supplied, the command returns
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a list of the identifiers for all existing
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event handlers created by the <B>after</B> command for this
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interpreter.
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If <I>id</I> is supplied, it specifies an existing handler;
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<I>id</I> must have been the return value from some previous call
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to <B>after</B> and it must not have triggered yet or been cancelled.
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In this case the command returns a list with two elements.
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The first element of the list is the script associated
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with <I>id</I>, and the second element is either
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<B>idle</B> or <B>timer</B> to indicate what kind of event
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handler it is.
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<P></DL>
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<P>
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The <B>after </B><I>ms</I> and <B>after idle</B> forms of the command
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assume that the application is event driven: the delayed commands
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will not be executed unless the application enters the event loop.
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In applications that are not normally event-driven, such as
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<B><A HREF="../UserCmd/tclsh.htm">tclsh</A></B>, the event loop can be entered with the <B><A HREF="../TkCmd/vwait.htm">vwait</A></B>
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and <B><A HREF="../TkCmd/update.htm">update</A></B> commands.
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<H3><A NAME="M11">SEE ALSO</A></H3>
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<B><A HREF="../TkCmd/bgerror.htm">bgerror</A></B>, <B><A HREF="../TkCmd/concat.htm">concat</A></B>, <B><A HREF="../TkCmd/update.htm">update</A></B>, <B><A HREF="../TkCmd/vwait.htm">vwait</A></B>
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<H3><A NAME="M12">KEYWORDS</A></H3>
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<A href="../Keywords/C.htm#cancel">cancel</A>, <A href="../Keywords/D.htm#delay">delay</A>, <A href="../Keywords/I.htm#idle callback">idle callback</A>, <A href="../Keywords/S.htm#sleep">sleep</A>, <A href="../Keywords/T.htm#time">time</A>
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<HR><PRE>
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<A HREF="../copyright.htm">Copyright</A> © 1990-1994 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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