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Diffstat (limited to 'tcl8.6/doc/error.n')
| -rw-r--r-- | tcl8.6/doc/error.n | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/tcl8.6/doc/error.n b/tcl8.6/doc/error.n new file mode 100644 index 0000000..c05f8b9 --- /dev/null +++ b/tcl8.6/doc/error.n @@ -0,0 +1,78 @@ +'\" +'\" Copyright (c) 1993 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 error n "" Tcl "Tcl Built-In Commands" +.so man.macros +.BS +'\" Note: do not modify the .SH NAME line immediately below! +.SH NAME +error \- Generate an error +.SH SYNOPSIS +\fBerror \fImessage\fR ?\fIinfo\fR? ?\fIcode\fR? +.BE + +.SH DESCRIPTION +.PP +Returns a \fBTCL_ERROR\fR code, which causes command interpretation to be +unwound. \fIMessage\fR is a string that is returned to the application +to indicate what went wrong. +.PP +The \fB\-errorinfo\fR return option of an interpreter is used +to accumulate a stack trace of what was in progress when an +error occurred; as nested commands unwind, +the Tcl interpreter adds information to the \fB\-errorinfo\fR +return option. If the \fIinfo\fR argument is present, it is +used to initialize the \fB\-errorinfo\fR return options and +the first increment of unwind information +will not be added by the Tcl interpreter. +In other +words, the command containing the \fBerror\fR command will not appear +in the stack trace; in its place will be \fIinfo\fR. +Historically, this feature had been most useful in conjunction +with the \fBcatch\fR command: +if a caught error cannot be handled successfully, \fIinfo\fR can be used +to return a stack trace reflecting the original point of occurrence +of the error: +.PP +.CS +catch {...} errMsg +set savedInfo $::errorInfo +\&... +\fBerror\fR $errMsg $savedInfo +.CE +.PP +When working with Tcl 8.5 or later, the following code +should be used instead: +.PP +.CS +catch {...} errMsg options +\&... +return -options $options $errMsg +.CE +.PP +If the \fIcode\fR argument is present, then its value is stored +in the \fB\-errorcode\fR return option. The \fB\-errorcode\fR +return option is intended to hold a machine-readable description +of the error in cases where such information is available; see +the \fBreturn\fR manual page for information on the proper format +for this option's value. +.SH EXAMPLE +.PP +Generate an error if a basic mathematical operation fails: +.PP +.CS +if {1+2 != 3} { + \fBerror\fR "something is very wrong with addition" +} +.CE +.SH "SEE ALSO" +catch(n), return(n) +.SH KEYWORDS +error, exception +'\" Local Variables: +'\" mode: nroff +'\" End: |