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author | William Joye <wjoye@cfa.harvard.edu> | 2018-12-25 17:45:11 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2018-12-25 17:45:11 (GMT) |
commit | 5f5fd2864a3193a8d5da12fcb92ba7379084c286 (patch) | |
tree | bcdca927ed2a7b05c647b9a6bfdfd4a7ca5c730e /tcl8.6/doc/bgerror.n | |
parent | 535baffcecf6e738102fc12cda0109bc963e150f (diff) | |
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update tcl/tk
Diffstat (limited to 'tcl8.6/doc/bgerror.n')
-rw-r--r-- | tcl8.6/doc/bgerror.n | 93 |
1 files changed, 0 insertions, 93 deletions
diff --git a/tcl8.6/doc/bgerror.n b/tcl8.6/doc/bgerror.n deleted file mode 100644 index 3644b3d..0000000 --- a/tcl8.6/doc/bgerror.n +++ /dev/null @@ -1,93 +0,0 @@ -'\" -'\" Copyright (c) 1990-1994 The Regents of the University of California. -'\" Copyright (c) 1994-1996 Sun Microsystems, Inc. -'\" -'\" See the file "license.terms" for information on usage and redistribution -'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. -'\" -.TH bgerror n 7.5 Tcl "Tcl Built-In Commands" -.so man.macros -.BS -'\" Note: do not modify the .SH NAME line immediately below! -.SH NAME -bgerror \- Command invoked to process background errors -.SH SYNOPSIS -\fBbgerror \fImessage\fR -.BE -.SH DESCRIPTION -.PP -Release 8.5 of Tcl supports the \fBinterp bgerror\fR command, -which allows applications to register in an interpreter the command -that will handle background errors in that interpreter. In older -releases of Tcl, this level of control was not available, and applications -could control the handling of background errors only by creating -a command with the particular command name \fBbgerror\fR in the -global namespace of an interpreter. The following documentation -describes the interface requirements of the \fBbgerror\fR command -an application might define to retain compatibility with pre-8.5 -releases of Tcl. Applications intending to support only -Tcl releases 8.5 and later should simply make use of \fBinterp bgerror\fR. -.PP -The \fBbgerror\fR command does not exist as built-in part of Tcl. Instead, -individual applications or users can define a \fBbgerror\fR -command (e.g. as a Tcl procedure) if they wish to handle background -errors. -.PP -A background error is one that occurs in an event handler or some -other command that did not originate with the application. -For example, if an error occurs while executing a command specified -with the \fBafter\fR command, then it is a background error. -For a non-background error, the error can simply be returned up -through nested Tcl command evaluations until it reaches the top-level -code in the application; then the application can report the error -in whatever way it wishes. When a background error occurs, the -unwinding ends in the Tcl library and there is no obvious way for Tcl -to report the error. -.PP -When Tcl detects a background error, it saves information about the -error and invokes a handler command registered by \fBinterp bgerror\fR -later as an idle event handler. The default handler command in turn -calls the \fBbgerror\fR command . -Before invoking \fBbgerror\fR, Tcl restores the -\fBerrorInfo\fR and \fBerrorCode\fR variables to their values at the -time the error occurred, then it invokes \fBbgerror\fR with the error -message as its only argument. Tcl assumes that the application has -implemented the \fBbgerror\fR command, and that the command will -report the error in a way that makes sense for the application. Tcl -will ignore any result returned by the \fBbgerror\fR command as long -as no error is generated. -.PP -If another Tcl error occurs within the \fBbgerror\fR command (for -example, because no \fBbgerror\fR command has been defined) then Tcl -reports the error itself by writing a message to stderr. -.PP -If several background errors accumulate before \fBbgerror\fR is -invoked to process them, \fBbgerror\fR will be invoked once for each -error, in the order they occurred. However, if \fBbgerror\fR returns -with a break exception, then any remaining errors are skipped without -calling \fBbgerror\fR. -.PP -If you are writing code that will be used by others as part of a -package or other kind of library, consider avoiding \fBbgerror\fR. -The reason for this is that the application programmer may also want -to define a \fBbgerror\fR, or use other code that does and thus will -have trouble integrating your code. -.SH "EXAMPLE" -.PP -This \fBbgerror\fR procedure appends errors to a file, with a timestamp. -.PP -.CS -proc bgerror {message} { - set timestamp [clock format [clock seconds]] - set fl [open mylog.txt {WRONLY CREAT APPEND}] - puts $fl "$timestamp: bgerror in $::argv '$message'" - close $fl -} -.CE -.SH "SEE ALSO" -after(n), errorCode(n), errorInfo(n), interp(n) -.SH KEYWORDS -background error, reporting -'\" Local Variables: -'\" mode: nroff -'\" End: |