49 lines
2.5 KiB
HTML
49 lines
2.5 KiB
HTML
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<HTML><HEAD><TITLE>Built-In Commands - error manual page</TITLE></HEAD><BODY>
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<H3><A NAME="M2">NAME</A></H3>
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error - Generate an error
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<H3><A NAME="M3">SYNOPSIS</A></H3>
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<B>error </B><I>message</I> ?<I>info</I>? ?<I>code</I>?<BR>
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<H3><A NAME="M4">DESCRIPTION</A></H3>
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Returns a TCL_ERROR code, which causes command interpretation to be
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unwound. <I>Message</I> is a string that is returned to the application
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to indicate what went wrong.
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<P>
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If the <I>info</I> argument is provided and is non-empty,
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it is used to initialize the global variable <B>errorInfo</B>.
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<B>errorInfo</B> is used to accumulate a stack trace of what
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was in progress when an error occurred; as nested commands unwind,
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the Tcl interpreter adds information to <B>errorInfo</B>. If the
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<I>info</I> argument is present, it is used to initialize
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<B>errorInfo</B> and the first increment of unwind information
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will not be added by the Tcl interpreter. In other
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words, the command containing the <B>error</B> command will not appear
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in <B>errorInfo</B>; in its place will be <I>info</I>.
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This feature is most useful in conjunction with the <B><A HREF="../TkCmd/catch.htm">catch</A></B> command:
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if a caught error cannot be handled successfully, <I>info</I> can be used
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to return a stack trace reflecting the original point of occurrence
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of the error:
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<PRE><B>catch {...} errMsg
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set savedInfo $errorInfo
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...
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error $errMsg $savedInfo</B></PRE>
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<P>
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If the <I>code</I> argument is present, then its value is stored
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in the <B>errorCode</B> global variable. This variable is intended
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to hold a machine-readable description of the error in cases where
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such information is available; see the <B><A HREF="../TkCmd/tclvars.htm">tclvars</A></B> manual
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page for information on the proper format for the variable.
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If the <I>code</I> argument is not
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present, then <B>errorCode</B> is automatically reset to
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``NONE'' by the Tcl interpreter as part of processing the
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error generated by the command.
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<H3><A NAME="M5">SEE ALSO</A></H3>
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<B><A HREF="../TkCmd/catch.htm">catch</A></B>, <B><A HREF="../TkCmd/tclvars.htm">tclvars</A></B>
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<H3><A NAME="M6">KEYWORDS</A></H3>
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<A href="../Keywords/E.htm#error">error</A>, <A href="../Keywords/E.htm#errorCode">errorCode</A>, <A href="../Keywords/E.htm#errorInfo">errorInfo</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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