error(3Tcl)

NAME
     error - Generate an error

SYNOPSIS
     error message ?info? ?code?


DESCRIPTION
     Returns a TCL_ERROR code, which causes command interpretation 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 containing the error
     command will not appear in errorInfo; in its place will be info.  This
     feature is most useful in conjunction 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