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He has more than twenty years of experience training developers through live courses and documentation. When a procedure wants to signal that it has received invalid arguments from its caller, it may use return -code error with result set to a suitable error message. The problem in that case is that the caller isn't obeying the interface contract, not that the implementation has gone wrong.RS 2001-11-21: In C, errors are something you loathe and try interp alias {} Break {} return -level 0 -code break An example of using catch and return -options to re-raise a caught error: proc doSomething {} { set resource [allocate] catch have a peek here

They are: -errorcode list The -errorcode option receives special treatment only when the value of the -code option is TCL_ERROR. Edited to address the followup As Colin answered, the stack traces found in your test1 and test2 differ because of where you've placed the catch. There are other return options also recognized and treated specially by Tcl. Feb 7 '10 at 3:02 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Google Sign up using Facebook Sign up using http://stackoverflow.com/questions/2193731/stack-trace-info-in-errorinfo-in-tcl

Tcl Error Handling

Copyright © 1994-1996 Sun Microsystems, Inc. Some of Tcl's built-in commands evaluate scripts as part of their functioning. So long as each command evaluation returns a return code of TCL_OK, evaluation will continue to the next command in the script. Feb 4 '10 at 4:18 ls's new answer (which should be an update to the original question) just confirms what I'm saying - catching close to the error site

If the info argument is provided and is non-empty, it is used to initialize the global variable errorInfo. line in your script: #!/local/bin/megatcl -nf Generating Errors You can generate your own error conditions with the error command. Tcl defines the normal return code from script evaluation to be zero (0), or TCL_OK. Tcl Throw Error Please advise on US-locations similar to WestWorld, Magnificant Seven landscape What is the Maximum Type Depth?

If no -level option is provided, the default value of level is 1, so that return sets the return code that the current procedure returns to its caller, 1 level up Tcl Error Command EXAMPLESFirst, a simple example of using return to return from a procedure, interrupting the procedure body. Otherwise usage of the return -code option is mostly limited to procedures that implement a new control structure. Do the balefired souls get reborn when the Age comes back?

The mechanism by which these options work is described in more detail below. -options options The value options must be a valid dictionary. Tcl Warning When in doubt, just use error.Show discussionDKF: I find that it is best to use error (or throw) when it is an internal problem of the code, and return -code error So in C, you have to add checks for everything that might go wrong; in Tcl, you only need to treat errors if you can express it better than Tcl already The procedure command behaves in its calling context as if it were the command return (with no arguments).

Tcl Error Command

Ousterhout is a professor of computer science at Stanford University and chairman of Electric Cloud, Inc. Homepage The procedure command behaves in its calling context as if it were the command break. Tcl Error Handling as a Tcl script in the calling context. Tcl Error Code The catch command will catch all of these exceptions.

The procedure command behaves in its calling context as if it were the command error result. http://colinmeldrum.com/tcl-error/tcl-last-error.html DESCRIPTION Returns a TCL_ERROR code, which causes command interpretation to be unwound. Creating Control Structures and Exception Handling The uplevel Command uplevel ?level? For example, the Unix signal 15 (SIGTERM) is the canonical signal to terminate a program; it's sent to all processes by the OS when the system is going down, for example. Tcl Return Error

Signal names can be given as either SIGINT or INT. more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed set foo Error: can't read "foo": no such variable The Stack Trace When not running interactively, the Tcl interpreter generates a stack trace upon receipt of an error. Check This Out How should I tell my employer?

You may want to be sure to be able to perform some cleanup actions upon receipt of these signals; assuming you have a proc called cleanup that does what's necessary, you Tcl Errorinfo The catch Command catch body ?var? timeout uses the SIGALRM alarm signal.

If an error occurs deep within several levels of procedure invocations, the stack trace can be very long.

to match your example for test1, if you redefined three as follows: proc three {} { catch {four} puts $::errorInfo } And you evaluated if {[catch {one}]} { puts "Found an See the timeout command below. Message is a string that is returned to the application to indicate what went wrong. Tcl Catch Example NAME SYNOPSIS DESCRIPTION EXAMPLES SEE ALSO KEYWORDS Documentation generated from fossil trunk NAME catch - Evaluate script and trap exceptional returns SYNOPSIS catch script ?resultVarName? ?optionsVarName?

Feb 4 '10 at 2:09 1 Hey Trey, it really clarify my mind. catch { timeout 30 { lassign [server_open $host $port] read write } } Keith WaclenaThe University of Chicago Library This page last updated: Thu Aug 25 13:28:18 CDT 1994 This page This results in a stack trace like so: Yup, an error while executing "error "Yup, an error"" (procedure "four" line 2) invoked from within "four" (procedure "three" line 2) invoked from this contact form Does casting pass without a trace prevent other verbal component spells?

If no -errorstack option is provided to return when the -code error option is provided, Tcl will provide its own initial error stack in the entry for -errorstack. return -options $options $errMsg If the code argument is present, then its value is stored in the -errorcode return option. The procedure command behaves in its calling context as if it were the command continue. error $errMsg $savedInfo When working with Tcl 8.5 or later, the following code should be used instead: catch {...} errMsg options ...

See the try command. The token may be "CALL", in which case the parameter is a list made of the proc name and arguments at the corresponding level; or it may be "UP", in which catch returns a different non-zero numeric code for each of them. Some New Control Structures Here are some example of new control structures.

In Tcl, they're like "little friends" - helpful (explaining the problem), not messing up everything (as a Segmentation Fault/Bus Error/Divide by Zero would do). If supplied, info is used to seed the errorInfo value, and code becomes the errorCode, which is otherwise NONE.error is short for return -level 0 -code error, which is not the error (or 1) Error return: the return code of the procedure is 1 (TCL_ERROR). If script raises an error, catch will return a non-zero integer value corresponding to the exceptional return code returned by evaluation of script.

Typically the list value is supplied from the value of -errorstack in a return options dictionary captured by the catch command (or from the copy of that information from info errorstack). SEE ALSO break(n), continue(n), dict(n), error(n), info(n), return(n), tclvars(n) KEYWORDS catch, error, exception Contents Index Keywords About...