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Early throw Discussion editThe following discussion was held before Tcl 8.6 added try/throw:throw: The logical opposite to catching is throwing. The output will go to stdout - the console from where you started the script. The standard ARITH, CHILD*, NONE, and POSIX only cover a fraction of all possible error conditions.Tcl syntaxCategory Debugging HomeRecent changesHelpWhoAmI/LogoutCreate new pageRandom pagePrevious pageNext pageAdd commentsEditHistoryEdit summaryReferences Page contents SeeAlso Description Generates a return exception condition. http://colinmeldrum.com/tcl-error/tcl-error-f5.html

return editJMN 2007-11-24:I've been in the habit of using the idiom:if {[catch { #somescript } result_or_errormsg]} { #handle error } else { #normal processing }However.. Stepping through a procedure[edit] To find out how exactly a proc works (and what goes wrong where), you can also register commands to be called before and after a command inside You can use the following step and interact procedures for this: proc step {name {yesno 1}} { set mode [expr {$yesno? "add" : "remove"}] trace $mode execution $name {enterstep leavestep} interact Using a trace, it is also possible to specify a condition once, and have it tested whenever a variable's value changes: proc assertt {varName condition} { uplevel 1 [list trace var

Tcl Error Command

The programmer can then decide what to do about those errors and act accordingly, instead of having the whole application come to a halt. error $errMsg $savedInfo If the code argument is present, then its value is stored in the errorCode global variable. In Java, you can have a variety of exceptions, each represented by a different class, that signal different types of error conditions. It's better practice to put separate "catch" commands around both the "puts" and the "close" commands to detect errors in either case and handle them appropriately.This is a different style of

What is Tk? This behavior can lead to problems like this:# I've got an open socket whose handle's stored in fid catch { puts $fid "Here's my last message." close $fid } errIf the Say if you want to see the values of variables x and y, just insert puts x:$x,y:$y (if the string argument contains no spaces, it needs not be quoted). Tcl Error Code See Also editbreakcontinuereturnerrormagic nameserrorCodeerrorInfoTcl performance: catch vs.

Getting Tcl/Tk Getting help Learning Tcl Tcl Dev Xchange About the Wiki Community Advocacy Conferences Chat, news, lists History Humor People Tcl websites Reference Companies Getting help Online books Online tutorials Tcl Error Handling The problems discussed include how to capture stderr, how to filter out prompts and transform an asynchronous interaction into a synchronous one with timeout mechanisms using vwait, how to link a Some useful things to do at such a debugging prompt: info level 0 ;# shows how the current proc was called info level ;# shows how deep you are in the https://www.tcl.tk/man/tcl/TclCmd/error.htm The return value of catch is the status return of the Tcl interpreter after it executes script If there are no errors in script, this value is 0.

And still somehow Zen buddhistic, if you deliberately use a non-existing command, and it does just the right thing... (Kevin Kenny introduced this trick in Tricky catch).In some cases, stack traces Tcl Catch Exec Description editGenerates an error with the specified message. Here is the modified code which does the same:set resource [some allocator] if {[set result [catch {some code with $resource} resulttext resultoptions]]} { # free the resource, ignore nested errors catch Trying isolated test cases interactively, and pasting the command into the editor when satisfied, can greatly reduce debugging time (there is no need to restart the application after every little change

Tcl Error Handling

If the info argument is provided and is non-empty, it is used to initialize the global variable errorInfo. try this The earlier found, the easier for the coder, so the golden rule "Test early. Tcl Error Command r+.MSW: Note that piping stderr and stdout simultaneously won't work for all operating systems. Tcl Catch Example Instead, exit the program; the language's shut-down code should handle the flushing and closing for you.

wiki.tcl.tk error Updated 2016-10-02 07:45:53 by dkf ▲ error, a built-in Tcl command, triggers an error state. http://colinmeldrum.com/tcl-error/tcl-error-out.html bodies, but when you add another line you might forget to add the braces. Catch Syntax catch script resultVarName In the above catch command syntax, script is the code to be executed, resultVarName is variable that holds the error or the result. One way to work around that is to redirect stderr, perhaps straight back to stderr: >@stderr.AMG: I prefer to construct the first argument to open thus: |[list progname arg1 arg2 arg3 Tcl Errorinfo

By using this site, you agree to the Terms of Use and Privacy Policy. Order does not matter here. Privacy policy About Wikibooks Disclaimers Developers Cookie statement Mobile view Tcl Built-In Commands NAME error - Generate an error SYNOPSIS error message ?info? ?code? Check This Out It is perfectly reasonable to catch "large" chunks:if { [ catch { puts $fid "Here's my last message." close $fid } err ] } { catch { close $fid } return

Caveat: mode a editDKF, et al:For mode a, Tcl seeks (seek()) to the end of the file immediately upon opening the file, and presumes that's good enough, but that can cause Tcl Return Error If you got all the lines written, that is good.On a problematic system, using the APPEND flag, which translates into the low-level O_APPEND flag to the PrivoxyWindowOpen() syscall, alters the semantics Silly example: % proc foo {} {bar x} % proc bar {input} {grill$input} % foo invalid command name "grillx" % set errorInfo invalid command name "grillx" while executing "grill$input" (procedure "bar"

EXAMPLE Generate an error if a basic mathematical operation fails: if {1+2 != 3} { error "something is very wrong with addition" } SEE ALSO catch, return KEYWORDS error, exception Copyright

This protects against whitespace embedded in the arguments from futzing up the works. One relevent excerpt from that documentation: If CREATE_ALWAYS and FILE_ATTRIBUTE_NORMAL are specified, CreateFile fails and sets the last error to ERROR_ACCESS_DENIED if the file exists and has the FILE_ATTRIBUTE_HIDDEN or FILE_ATTRIBUTE_SYSTEM Someone with Solaris 8 and 9 might want to test this (don't have access to one atm). Tcl Throw Error There are several pages dedicated to these issues on the AlphaTcl Wiki.see notably Alpha and Unix, which is an overview page.

too hot!"} Where the error occurred is evident from::errorInfo, which will look a bit clearer (no mention of the error command) if you code if {$temperature > 100} {return -code error Command Pipelines editCommand pipelines executed by open generate errors exactly as described for exec, and close returns the error when it receives the channel returned by open as an argument. Description editreturn creates an options dictionary which made available via catch and try. this contact form command one level up, i.e.

The errorCode variable[edit] In addition, there is the errorCode variable that returns a list of up to three elements: category (POSIX, ARITH, ...) abbreviated code for the last error human-readable error Each procedure adds some information about the problem to the report. But I couldn't find an easy solution to that quirk in this breakfast fun project - backslashing the $condition in the assertt code sure didn't help. Even though there's no problem with your command line, one day you might change it, perhaps to use a parameter to your proc as an argument.

Documentation editofficial referenceRunning other programs from Tcl - exec, openTIP 183: Add a Binary Flag to open Description editIf b is appended to mode it has the same effect as fconfigure Use at your own risk, of course...:^) The "debuggee" contains in my experiments the following code, in addition to its own: proc remo_server {{port 3456}} { set sock [socket -server remo_accept Roll Your Own Pipeline editPYK 2015-04-27: As of 8.6 it's possible to close only one side of a channel. If the info argument is present, it is used to initialize the -errorinfo return options and the first increment of unwind information will not be added by the Tcl interpreter.

I had to redirect stuff to files and watch the files to follow the output (invoked program in question was cvs). However, there is no -ignorestderr option. Examples: if {$username eq ""} {error "please specify a user name"} if [catch {open $filename w} fp] { error "$filename is not writable" } One reason for errors can be an Silly example: % proc foo {} {bar x} % proc bar {input} {grill$input} % foo invalid command name "grillx" % set errorInfo invalid command name "grillx" while executing "grill$input" (procedure "bar"

Since the console is a Tk text widget, you can use all text widget commands and options on it (for example, changing colors, bindings...). A Tcl proc can also generate an error status condition. 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. Both must have an event loop running (which is true when Tk runs, or when started with e.g.

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).