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markom |
'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: @(#) $Id: error.n,v 1.1.1.1 2002-01-16 10:25:24 markom Exp $
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'\"
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.so man.macros
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.TH error n "" Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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error \- Generate an error
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.SH SYNOPSIS
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\fBerror \fImessage\fR ?\fIinfo\fR? ?\fIcode\fR?
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.BE
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.SH DESCRIPTION
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.PP
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Returns a TCL_ERROR code, which causes command interpretation to be
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unwound. \fIMessage\fR is a string that is returned to the application
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to indicate what went wrong.
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.PP
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If the \fIinfo\fR argument is provided and is non-empty,
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it is used to initialize the global variable \fBerrorInfo\fR.
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\fBerrorInfo\fR 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 \fBerrorInfo\fR. If the
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\fIinfo\fR argument is present, it is used to initialize
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\fBerrorInfo\fR 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 \fBerror\fR command will not appear
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in \fBerrorInfo\fR; in its place will be \fIinfo\fR.
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This feature is most useful in conjunction with the \fBcatch\fR command:
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if a caught error cannot be handled successfully, \fIinfo\fR 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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.CS
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\fBcatch {...} errMsg
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set savedInfo $errorInfo
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\&...
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error $errMsg $savedInfo\fR
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.CE
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.PP
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If the \fIcode\fR argument is present, then its value is stored
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in the \fBerrorCode\fR 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 \fBtclvars\fR manual
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page for information on the proper format for the variable.
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If the \fIcode\fR argument is not
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present, then \fBerrorCode\fR 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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.SH KEYWORDS
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error, errorCode, errorInfo
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