tcl7.6 User Commands - error
NAME
error - Generate an error
SYNOPSIS
error message ?info? ?code?
DESCRIPTION
Returns a TCL_ERROR code, which causes command interpreta-
tion to be unwound. Message is a string that is returned to
the application to indicate what went wrong.
If the info argument is provided and is non-empty, it is
used to initialize the global variable errorInfo. errorInfo
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 errorInfo. If the info
argument is present, it is used to initialize errorInfo and
the first increment of unwind information will not be added
by the Tcl interpreter. In other words, the command con-
taining the error command will not appear in errorInfo; in
its place will be info. This feature is most useful in con-
junction with the catch command: if a caught error cannot
be handled successfully, info can be used to return a stack
trace reflecting the original point of occurrence of the
error:
catch {...} errMsg
set savedInfo $errorInfo
...
error $errMsg $savedInfo
If the code argument is present, then its value is stored in
the errorCode global variable. This variable is intended to
hold a machine-readable description of the error in cases
where such information is available; see the tclvars manual
page for information on the proper format for the variable.
If the code argument is not present, then errorCode is
automatically reset to ``NONE'' by the Tcl interpreter as
part of processing the error generated by the command.
KEYWORDS
error, errorCode, errorInfo