Program termination

Program termination
You are encouraged to solve this task according to the task description, using any language you may know.

Show the syntax for a complete stoppage of a program inside a conditional. This includes all threads/processes which are part of your program.

Explain the cleanup (or lack thereof) caused by the termination (allocated memory, database connections, open files, object finalizers/destructors, run-on-exit hooks, etc.). Unless otherwise described, no special cleanup outside that provided by the operating system is provided.

Ada

Ada programs execute in one or more tasks. All tasks created during the execution of a program depend in a hierarchical manner on the task that create them, except for the environment task which executes the "main" procedure for the program. Each task will abort (terminate abnormally) if the task upon which it depends is aborted. This approach to task termination is not recommended because it does not allow tasks to terminate in a known state.

However, this Rosetta Code task requires a simple stoppage of the program including all tasks. The simple way to achieve this is to abort the environment task.

with Ada.Task_Identification;  use Ada.Task_Identification;
 
procedure Main is
   -- Create as many task objects as your program needs
begin
   -- whatever logic is required in your Main procedure
   if some_condition then
      Abort_Task (Current_Task);
   end if;
end Main;

Aborting a task with Abort_Task is equivalent to abort statement, which is not used here because the environment task object is anonymous. The semantics of abort is as follows:

• Abort is deferred until certain unbreakable actions are accomplished. These are protected actions on shared objects, initialization, assignment, and finalization of controlled objects, waiting for dependent tasks to be aborted;
• Local objects of the task are finalized;
• The tasks dependent on the aborted task are aborted.
• The state of external files will depend on the OS

The above is a preemptive way to abort tasks, which is not recommended to use, unless you firmly know what you are doing. A standard approach to such termination is either (or a combination of):

• to provide an entry in each task created by the environment task which, when called by the task upon which it depends, causes the called task to terminate in a known state;
• to provide "terminate" alternative open in each of such tasks.

In both cases the task objects are made local or otherwise destroyed upon completion of the main task. Note that destruction of a task always waits for its termination. If the task refuses to terminate it deadlocks.

With the first approach:

procedure Main is
   -- Create as many task objects as your program needs
begin
   -- whatever logic is required in your Main procedure
   if some_condition then
      -- for each task created by the Main procedure
      The_task.Stop;
      -- end the Main procedure
      return;  -- actually, this is not needed
   end if;
end Main;

A task might look like:

task body Some_Task is
begin
   loop
      select
         -- Some alternatives
         ...
      or accept Stop do
            -- Some cleanup while holding the caller is here
         end Stop;
            -- A cleanup asynchronous to the caller is here
         exit; -- We are through
      end select
   end loop;
end Some_Task;

With the second approach one simply returns from Main and all tasks are terminated by selecting the terminate alternative. Such tasks might look like:

task body Some_Task is
begin
   loop
      select
         -- Some alternatives
         ...
      or terminate; -- We are through
      end select
   end loop;
end Some_Task;

Aime

void
f1(integer a)
{
    if (a) {
	exit(1);
    }
}
 
integer
main(void)
{
    f1(3);
 
    return 0;
}

ALGOL 68

The label "stop" appears at the start of the standard-postlude and can be invoked to terminate any program.

IF problem = 1 THEN
   stop
FI

The standard-postlude closes any opens files and basically wraps up execution.

AWK

if(problem)exit 1

AppleScript

AppleScript doesn't include a built-in command for immediate script termination. The return command can be used to exit the main run handler, but will not force termination of the entire script from another handler/function.

on run
	If problem then return
end run

It's possible to simulate an immediate program termination from within any handler by throwing a user error, but this will force a modal dialog (AppleScript Error) to appear announcing the error. Such a dialog cannot be bypassed, and the script immediately quits upon user acknowledgement.

on run
	f()
	display dialog "This message will never be displayed."
end run
 
on f()
	error
end f

Memory is automatically managed and reclaimed by AppleScript.

AutoHotkey

If (problem)
  ExitApp

AutoIt

Then Endif is entirely unnecessary, but it is good form.

If problem Then
  Exit
Endif

BASIC

Works with: QuickBasic version 4.5

IF problem = 1 THEN
   END
END IF

Applesoft BASIC

10  IF 1 THEN  STOP

BASIC256

if not more then end

Locomotive Basic

10 IF 1 THEN END

ZX Spectrum Basic

The ZX Spectrum has a STOP command, rather than an END command:

10 LET a = 1: LET b = 1
20 IF a = b THEN GO TO 9995
9995 STOP

Batch File

if condition exit

In Windows batch files this doesn't need to exit the program but instead can also just exit a subroutine. exit /b can also be used alternatively if a return value if desired.

BBC BASIC

      IF condition% THEN QUIT

Only QUIT fully terminates the program. END and STOP stop execution and return control to the immediate-mode prompt; END closes all open files, but STOP does not.

Bracmat

From infinite loops (such as the read-eval-print loop that Bracmat enters when run in interactive mode) the program can only exit cleanly by evaluating a closing parenthesis followed by an affirmative y, Y, j or J. Thus, at the Bracmat prompt you type the closing parenthesis, a y and then press enter. From within Bracmat code, you force an exit by evaluating get'(")y",MEM). If Bracmat is linked to another program (e.g. as a Java Native Interface library), it is better to turn off the possibility to exit Bracmat, as that normally would cause the main program to crash. There is a C preprocessor macro that disables exiting.

If there are no infinite loops in Bracmat code, the Bracmat program will ultimately terminate in a natural way.

C

#include <stdlib.h>
/* More "natural" way of ending the program: finish all work and return
   from main() */
int main(int argc, char **argv)
{
  /* work work work */
     ...
  return 0;  /* the return value is the exit code. see below */
}
 
if(problem){
  exit(exit_code);
  /* On unix, exit code 0 indicates success, but other OSes may follow
     different conventions.  It may be more portable to use symbols
     EXIT_SUCCESS and EXIT_FAILURE; it all depends on what meaning
     of codes are agreed upon.
  */
}

The atexit() function (also in stdlib.h) can be used to register functions to be run when the program exits. Registered functions will be called in the reverse order in which they were registered.

#include <stdlib.h>
 
if(problem){
  abort();
}

Unlike exit(), abort() will not do any cleanup other than the normal OS one. Also, it may cause other actions like producing a core dump or starting a debugger.

To end not just the current process, but all processes in the same group, do

exit_group();

C++

There are several ways to terminate a program. The following is mostly the same as in C:

#include <cstdlib>
 
void problem_occured()
{
  std::exit(EXIT_FAILURE);
}

The argument is the return value passed to the operating system. Returning 0 or the EXIT_SUCCESS signals successful termination to the calling process, EXIT_FAILURE signals failure. The meaning of any other value is implementation defined.

On calling std::exit, all functions registered with std::atexit are called, and the destructors of all objects at namespace scope, as well as of all static objects already constructed, are called. However the destructors of automatic objects (i.e. local variables) are not called (and of course, objects allocated with new will not be destructed as well, except if one of the called destructors destroys them). Due to this inconsistency calling std::exit is often not a good idea.

#include <cstdlib>
 
void problem_occured()
{
  std::abort();
}

Unlike std::exit, std::abort will not do any cleanup other than the normal OS one. Also, it may cause other actions like producing a core dump or starting a debugger.

#include <exception>
 
void problem_occured()
{
  std::terminate();
}

The function std::terminate is what is automatically called when certain exception related failures happen. However it also can be called directly. By default it just calls abort, but unlike abort, its behaviour can be overridden with std::set_terminate (but it still must terminate the program in one way or anouther). Thererfore the amount of cleanup it does depends on whether it was overridden, and what the overridden function does.

Note that returning a value from main is mostly equivalent to calling std::exit with the returned value, except that automatic variables are correctly destructed. If one wants to return from an inner function, while still doing complete cleanup, a solution is to throw an exception caught in main (this will call the destructors of non-main local variables during stack unwinding), and to then return normally from main (which will destruct all automatic objects in main, and then do the cleanup like std::exit.

C#

if (problem)
{
   Environment.Exit(1);
}

Clojure

Translation of: Java

The call System.exit does not finalize any objects by default. This default is to keep the program thread-safe. From the javadocs for the method to change this default: "may result in finalizers being called on live objects while other threads are concurrently manipulating those objects, resulting in erratic behavior or deadlock."

(if problem
   (. System exit integerErrorCode))
   ;conventionally, error code 0 is the code for "OK",
   ; while anything else is an actual problem
   ;optionally: (-> Runtime (. getRuntime) (. exit integerErrorCode))
}

You can use (-> Runtime (. getRuntime) (. addShutdownHook myThread)) to add threads which represent actions to be run when the program exits.

This one does not perform cleanup:

(if problem
   (-> Runtime (. getRuntime) (. halt integerErrorCode)))
   ; conventionally, error code 0 is the code for "OK",
   ; while anything else is an actual problem
 

Common Lisp

Many Common Lisp implementations provide a function named quit or sometimes exit which will exit the Lisp system; its parameters and the package it is in vary, but here are some implementations' versions, with a Unix-style exit status argument, and a fallback:

(defun terminate (status)
  #+sbcl     (sb-ext:quit      :unix-status status)    ; SBCL
  #+ccl      (   ccl:quit      status)                 ; Clozure CL
  #+clisp    (   ext:quit      status)                 ; GNU CLISP
  #+cmu      (  unix:unix-exit status)                 ; CMUCL
  #+abcl     (   ext:quit      :status status)         ; Armed Bear CL
  #+allegro  (  excl:exit      status :quiet t)        ; Allegro CL
  (cl-user::quit))           ; Many implementations put QUIT in the sandbox CL-USER package.

There is no standard form because the Common Lisp standard does not assume the presence of an operating system outside of the Lisp environment to exit to.

What cleanup will be performed varies. Some implementations have at-exit hooks. SBCL will unwind the stack and execute any unwind-protects (like finally in other languages) it encounters, unless :recklessly-p t is specified.

Delphi/Pascal

System.Halt;

or

System.Halt(1); // Optional exit code

E

Exit indicating successful completion:

if (true) {
    interp.exitAtTop()
}

Exit indicating some problem:

if (true) {
    interp.exitAtTop("because the task said so")
}

Both of these have the same effect with regard to cleanup as as reaching the end of the main program. [To do: Find out what effect that is.]

Erlang

Polite

% Implemented by Arjun Sunel
if problem ->
	exit(1).
 

As soon as possible

 
% Implemented by Arjun Sunel
if problem ->
	halt().
 

Forth

debug @
if   QUIT  \ quit back to the interpreter
else BYE   \ exit forth environment completely (e.g. end of a Forth shell script)
then

Fortran

In Fortran STOP stops the execution of the main process and its "children" (tested with OpenMP; if using POSIX threads, I think the stop behaves almost like C exit). Allocated memory or any other resource except opened file (which are closed) is not cleaned up.

IF (condition) STOP [message] 
! message is optional and is a character string.
! If present, the message is output to the standard output device.

F#

open System
 
if condition then
    Environment.Exit 1

Gema

Terminate with an error message and a non-zero status code if "Star Trek" is found in the input stream.

Star Trek=@err{found a Star Trek reference\n}@abort

Go

Operating system resources such as memory and file handles are generally released on exit automatically, but this is not specified in the language definition. Proceses started with os.StartProcess or exec.Run are not automatically terminated by any of the techniques below and will continue to run after the main program terminates.

Return statement

Basically, a return statement executed from anywhere in main() terminates the program.

func main() {
    if problem {
        return
    }
}

Deferred functions are run when the enclosing function returns, so in the example below, function paperwork is run. This is the idiomatic mechanism for doing any kind of necessary cleanup.

Other goroutines are terminated unceremoniously when main returns. Below, main returns without waiting for pcj to complete.

The tantalizingly named SetFinalizer mechanism is also not invoked on program termination. It is designed for resource reclamation in long-running processes, not for program termination.

Returns from functions other than main do not cause program termination. In particular, return from a goroutine simply terminates that one goroutine, and not the entire program.

package main
 
import (
    "fmt"
    "runtime"
    "time"
)
 
const problem = true
 
func main() {
    fmt.Println("main program start")
 
    // this will get run on exit
    defer paperwork()
 
    // this will not run to completion
    go pcj()
 
    // this will not get run on exit
    rec := &requiresExternalCleanup{"external object"}
    runtime.SetFinalizer(rec, cleanup)
 
    if problem {
        fmt.Println("main program returning")
        return
    }
}
 
func paperwork() {
    fmt.Println("i's dotted, t's crossed")
}
 
func pcj() {
    fmt.Println("there's uncle Joe")
    time.Sleep(1e10)
    fmt.Println("movin kinda slow")
}
 
type requiresExternalCleanup struct {
    id string
}
 
func cleanup(rec *requiresExternalCleanup) {
    fmt.Println(rec.id, "cleanup")
}

Output:

main program start
main program returning
there's uncle Joe
i's dotted, t's crossed

Runtime.Goexit

Runtime.Goexit works like a return statement in main(), but can be called from any function called from main, at any function call depth. More accurately, Goexit terminates the goroutine that calls it, calling all deferred functions in the process. Thus if the goroutine is the goroutine running main, the program exits.

Os.Exit

Os.Exit causes its argument to be returned to the operating system as a program exit code. Unlike the return statement and runtime.Goexit, os.Exit exits promptly and does not run deferred functions.

func main() {
    fmt.Println("main program start")
 
    // this will not get run on os.Exit
    defer func() {
        fmt.Println("deferred function")
    }()
 
    if problem {
        fmt.Println("main program exiting")
        os.Exit(-1)
    }
}

Output:

main program start
main program exiting

Panic

Panics have some similarities to exceptions in other languages, including that there is a recovery mechanism allowing program termination to be averted. When the program terminates from panic however, it prints the panic value and then a stack trace for all goroutines.

Like the return statement, panic runs deferred functions. It run functions deferred from the current function, but then proceeds to unwind the call stack of the goroutine, calling deferred functions at each level. It does this only in the goroutine where panic was called. Deferred functions in other goroutines are not run and if panicking goes unrecovered and the program terminates, all other goroutines are terminated abruptly.

func pcj() {
    fmt.Println("at the junction")
    defer func() {
        fmt.Println("deferred from pcj")
    }()
    panic(10)
}
 
func main() {
    fmt.Println("main program start")
    defer func() {
        fmt.Println("deferred from main")
    }()
    go pcj()
    time.Sleep(1e9)
    fmt.Println("main program done")
}

Output:

main program start
at the junction
deferred from pcj
panic: 10
(and the stack trace follows)

GW-BASIC

10 IF 1 THEN STOP

Groovy

See Java for a more complete explanation.

Solution #1:

if (problem) System.exit(intExitCode)

Solution #1:

if (problem) Runtime.runtime.halt(intExitCode)

Haskell

import Control.Monad
import System.Exit
 
when problem do
    exitWith ExitSuccess                    -- success
    exitWith (ExitFailure integerErrorCode) -- some failure with code
    exitSuccess                             -- success; in GHC 6.10+
    exitFailure                             -- generic failure

The above shows how to exit a thread. When the main thread exits, all other threads exit, and the return code in the exit call is the return code of the program. When any thread other than the main thread exits, only it is stopped, and if the exit code is not ExitSuccess, it is printed.

HicEst

ALARM( 999 )

This closes windows, dialogs, files, DLLs, and frees allocated memory. Script editing is resumed on next start.

Icon and Unicon

exit(i)          # terminates the program setting an exit code of i
stop(x1,x2,..)   # terminates the program writing out x1,..; if any xi is a file writing switches to that file
runerr(i,x)      # terminates the program with run time error 'i' for value 'x'

J

Given condition, an integer which is zero if everything's OK (and we should NOT exit), or a non-zero exit code if there's a problem (and we should exit), then:

Tacit version:

2!:55^:] condition

Explicit version:

3 : 'if. 0~: condition do. 2!:55 condition end.'

Java

The call System.exit does not finalize any objects by default. This default is to keep the program thread-safe. From the javadocs for the method to change this default: "may result in finalizers being called on live objects while other threads are concurrently manipulating those objects, resulting in erratic behavior or deadlock."

if(problem){
   System.exit(integerErrorCode); 
   //conventionally, error code 0 is the code for "OK",
   // while anything else is an actual problem
   //optionally: Runtime.getRuntime().exit(integerErrorCode);
}

You can use Runtime.getRuntime().addShutdownHook(myThread); to add threads which represent actions to be run when the program exits.

This one does not perform cleanup:

if(problem){
   Runtime.getRuntime().halt(integerErrorCode); 
   //conventionally, error code 0 is the code for "OK",
   // while anything else is an actual problem
}

JavaScript

Works with: SpiderMonkey

The quit() function exits the shell.

if (some_condition) 
    quit();

Liberty BASIC

If any files or devices are still open when execution is terminated, then Liberty BASIC will close them and present a dialog expressing this fact.

The STOP statement is functionally identical to END and is interchangable. Also, make sure that when a program is finished running that it terminates properly with an END statement. Otherwise the program's windows may all be closed, giving the illusion that it has stopped running, but it will still be resident in memory and may still consume processor resources.

The following is functional. Better practice is to instead jump to commands or subs to close known open files, windows etc, avoiding error messages as above.

if 2 =2 then end

Logo

Works with: UCB Logo

bye   ; exits to shell
 
throw "toplevel  ; exits to interactive prompt
 
pause      ; escapes to interactive prompt for debugging
continue   ; resumes after a PAUSE

Lua

if some_condition then 
    os.exit( number )
end

M4

beginning
define(`problem',1)
ifelse(problem,1,`m4exit(1)')
ending

Output:

beginning

Mathematica

If[problem, Abort[]];

Kernels stop all computation after "Abort[]" command. But the kernels are still operational, and all definitions are still available. Note that an Abort[] can be caught by a calling function using CheckAbort, in which case the computation will continue at that place.

Quit[]

This will completely quit the kernel. All definitions will be lost. Since this terminates the actual kernel process, this will also free all resources used by that kernel (especially memory). Note however that if the kernel is interactively used through a notebook, the notebook still remains operable.

MATLAB

if condition
    return
end

There is no special way to stop a program. You can terminate it by calling return.

if condition
    quit
end

The quit function runs the MATLAB script finish.m, if it exists, and terminates MATLAB completely.

Maxima

/* Basically, it's simply quit() */
 
block([ans], loop, if (ans: read("Really quit ? (y, n)")) = 'y
                   then quit()
                   elseif ans = 'n then (print("Nice choice!"), 'done)
                   else (print("I dont' understand..."), go(loop)));

МК-61/52

ИП0	x=0	04	С/П	...

Condition of termination is Р0 = 0.

NetRexx

NetRexx's exit statement invokes Java's System.exit() so job termination is handled in the same way as any other Java program. (See Java above.)

/* NetRexx */
options replace format comments java crossref symbols nobinary
 
extremePrejudice = (1 == 1)
if extremePrejudice then do
  exit extremePrejudice
  end
 
return
 

Nimrod

if problem:
  quit(QuitFailure)

Objeck

The code below, will terminate a program without any cleanup.

if(problem) {
  Runtime->Exit(1);
};

OCaml

if problem then
  exit integerErrorCode;
  (* conventionally, error code 0 is the code for "OK",
     while anything else is an actual problem *)

The at_exit function can be used to register functions to be run when the program exits. Registered functions will be called in the reverse order in which they were registered.

Oz

if Problem then {Application.exit 0} end

All threads exit. All processes (local and remote) exit unless they were created with detach:true. Finalizers are not executed (unless enforced with {System.gcDo}).

PARI/GP

if(stuff, quit)

Perl

if ($problem) {
    exit integerErrorCode;
    # conventionally, error code 0 is the code for "OK"
    #  (you can also omit the argument in this case)
    # while anything else is an actual problem
}

exit() will run any cleanup code that is in an END block.

Perl 6

if $problem { exit $error-code }

An exit runs all appropriate scope-leaving blocks such as LEAVE, KEEP, or UNDO, followed by all END blocks, followed by all destructors that do more than just reclaim memory, and so cannot be skipped because they may have side effects visible outside the process. If run from an embedded interpreter, all memory must also be reclaimed. (Perl 6 does not yet have a thread-termination policy, but will need to before we're done.)

PHP

if (problem)
    exit(1);

The register_shutdown_function() function can be used to register functions to be run when the program exits.

PicoLisp

Calling 'bye', optionally with a numeric code, terminates the program.

This will execute all pending 'finally' expressions, close all open files and/or pipes, flush standard output, and execute all expressions in the global variable '*Bye' before exiting.

(push '*Bye '(prinl "Goodbye world!"))
(bye)

Output:

Goodbye world!
$

PL/I

STOP; /* terminates the entire program */
      /* PL/I does any required cleanup, such as closing files. */

STOP THREAD (tiger); /* terminates only thread "tiger". */

SIGNAL FINISH; /* terminates the entire program.   */
               /* PL/I does any required cleanup,  */
               /* such as closing files.           */

Pop11

if condition then
    sysexit();
endif;

PostScript

There are two ways which differ slightly:

condition {stop} if

will terminate a so-called stopped context which is a way of executing a block of code and catching errors that occur within. Any user program will always run in such a context and therefore be terminated upon calling stop

Neither the operand stack nor the dictionary stack are touched or cleaned up when calling stop. Anything pushed onto either stack will remain there afterwards.

condition {quit} if

will terminate the PostScript interpreter. This is definitely a way to stop the current program but since an interpreter can run multiple programs at the same time, this should rarely, if ever, be used.

PowerShell

if (somecondition) {
    exit
}

This ends the scope for any non-global variables defined in the script. No special cleanup is performed.

Prolog

Terminate Prolog execution. Open files are closed. Exits the Interpreter.

halt.

Terminate Prolog execution but don't exit the Interpreter.

abort.

PureBasic

This will free any allocated memory, close files and free other resources (i.e. windows, gadgets, threads, space for variable, etc.) that were set aside during execution of any PureBasic commands in the program.

If problem = 1
   End
EndIf

It is possible to also access outside resources (i.e. via an OS API or linked library), and those items may or may not be cleaned up properly.

Python

Polite

import sys
if problem:
    sys.exit(1)

The atexit module allows you to register functions to be run when the program exits.

As soon as possible

(Signals the underlying OS to abort the program. No cleanup is performed)

import os
if problem:
    os.abort()

R

if(problem) q(status=10)

Racket

Racket has an "exit" function that can be used to exit the Racket process, possibly returning a status code.

 
#lang racket
(run-stuff)
(when (something-bad-happened) (exit 1))
 

In addition, Racket has "custodians", which are objects that are used to manage a bunch of dynamically allocated resources (ie, open files, running threads). This makes it easy to run some code and conveniently kill it with all related resources when needed, without exiting from the whole process. It is common to use this facility in servers, where each handler invocation is wrapped in a new custodian that is shut down when its client interaction is done. For example:

 
#lang racket
(parameterize ([current-custodian (make-custodian)])
  (define (loop) (printf "looping\n") (sleep 1) (loop))
  (thread loop) ; start a thread under the new custodian
  (sleep 5)
  ;; kill it: this will kill the thread, and any other opened resources
  ;; like file ports, network connections, etc
  (custodian-shutdown-all (current-custodian)))
 

REBOL

The quit word stops all evaluation, releases operating system resources and exits the interpreter.

if error? try [6 / 0] [quit]

A return value can be provided to the operating system:

if error? try [dangerous-operation] [quit/return -12]

Because of REBOL's tightly integrated REPL, you can also use q to do the same thing.

if error? try [something-silly] [q/return -12]

Since GUI programs are often developed from the REPL, a special halt word is provided to kill the GUI and return to the REPL. No cleanup is done and the GUI is still displayed (although halted). You can restart it with the do-events word.

view layout [button "stopme" [halt]]

Retro

problem? [ bye ] ifTrue

REXX

In REXX, the REXX interpreter takes care of the closing of any open files (or any I/O streams), as well as any memory management (cleanup).

/*REXX program showing five ways to perform a REXX program termination. */
 
  /*─────1st way────────────────────────────────────────────────────────*/
exit
 
 
  /*─────2nd way────────────────────────────────────────────────────────*/
exit  (expression)     /*Note:  the "expression" doen't need parenthesis*/
                       /*"expression"  is any REXX expression.          */
 
 
  /*─────3rd way────────────────────────────────────────────────────────*/
return                 /*which returns to this program's invoker.  If   */
                       /*this is the main body  (and not a subroutine), */
                       /*the REXX interpreter terminates the program.   */
 
 
  /*─────4th way────────────────────────────────────────────────────────*/
return (expression)    /* [See the note above concerning parenthesis.]  */
 
 
  /*─────5th way────────────────────────────────────────────────────────*/
    /*control*/
    /*   │   */        /*if there is no EXIT and program control "falls */
    /*   │   */        /*through" to the "bottom" (end) of the program, */
    /*   │   */        /*an   EXIT   is simulated and the program is    */
    /*   │   */        /*terminated.                                    */
    /*   ↓   */
    /* e-o-f */        /* e-o-f   =   end-of-file.                      */

Ruby

if problem
    exit(1)
end

or

if problem
    abort # equivalent to exit(1)
end

You can use at_exit { ... } to register a block of code which will be run when the program exits. Registered handlers will be called in the reverse order in which they were registered.

Slate

problem ifTrue: [exit: 1].

Scheme

Works with: Scheme version R⁶RS

(if problem
  (exit)) ; exit successfully

or

(if problem
  (exit #f)) ; exit unsuccessfully

or

(if problem
  (exit some-value)) ; converts "some-value" into an appropriate exit code for your system

Seed7

When a program is stopped with exit(PROGRAM) allocated memory is freed and open files are closed,

$ include "seed7_05.s7i";
 
const proc: main is func
  begin
    # whatever logic is required in your main procedure
    if some_condition then
      exit(PROGRAM);
    end if;
  end func;

SNOBOL4

Conditional transfer to the required END label causes immediate termination and normal cleanup. In this example, if condition succeeds (is true), the value of errlevel is assigned to the &code keyword as the exit status of the program, and the :s( ) goto transfers control to END.

        &code = condition errlevel :s(end)

Standard ML

No cleanup is performed.

if problem then
  OS.Process.exit OS.Process.failure
  (* valid status codes include OS.Process.success and OS.Process.failure *)
else
  ()

The OS.Process.atExit function can be used to register functions to be run when the program exits. Registered functions will be called in the reverse order in which they were registered.

Tcl

The language runtime (in C) includes a mechanism for cleaning up open resources when the application quits, but access to this is not exposed at script level; extension packages just register with it automatically when required. At the script level, all that is needed to make the program terminate is the exit command:

if {$problem} {
    # Print a “friendly” message...
    puts stderr "some problem occurred"
    # Indicate to the caller of the program that there was a problem
    exit 1
}

Alternatively, in a top-level script but not an event handler:

if {$problem} {
    error "some problem occurred"
}

TI-83 BASIC

  :Stop

TI-89 BASIC

Prgm
  ...
  Stop
  ...
EndPrgm

TUSCRIPT

$$ MODE TUSCRIPT
IF (condition==1) STOP
-> execution stops and message:
IF (condition==2) ERROR/STOP "condition ",condition, " Execution STOP "

Unlambda

`ei

Note: the argument to the e function is the return value of the program; however many implementation simply ignore it.

There are no objects to be cleaned up.

UNIX Shell

Works with: Bourne Shell

#!/bin/sh
 
a='1'
b='1'
if [ "$a" -eq "$b" ]; then
  exit 239    # Unexpected error
fi
exit 0    # Program terminated normally

Vedit macro language

if (#99 == 1) { Return }        // Exit current macro. Return to calling macro.
if (#99 == 2) { Break_Out() }   // Stop all macro execution and return to command mode.
if (#99 == 3) { Exit }          // Exit Vedit. Prompt for saving any changed files.
if (#99 == 4) { Exit(4) }       // As above, but return specified value (instead of 0) to OS
if (#99 == 5) { Xall }          // Exit Vedit. Save changed files without prompting.
if (#99 == 6) { Qall }          // Exit Vedit. Do not save any files.

Return or Break_Out() do not perform any cleanup. If needed, cleanup has to be done in the macro before exit. Special locked-in macro can be used to perform cleanup in case user presses Break key.

When exit from Vedit is done, all the cleanup is performed automatically. Note, however, that if Edit Restore is enabled or a project is open, the session state is saved. In this case, if your macro does not do cleanup, you may eventually run out of free text registers, and you have to do manual cleanup.

VBScript

No matter how deep you're in, wscript.quit will get you out.

dim i, j
j = 0
do
    for i = 1 to 100
        while j < i
            if i = 3 then
                wscript.quit
            end if
        wend
    next
loop

Visual Basic

While the example listed under BASIC will work unaltered, it is a terrible idea to use the End keyword in VB. Doing so will cause the immediate termination of the program without any clean up -- forms and other things are left loaded in memory.

When the app needs to end, for whatever reason, problem or not, it's always a good idea to unload the forms first.

Sub Main()
    '...
    If problem Then
        For n& = Forms.Count To 0 Step -1
            Unload Forms(n&)
        Next
        Exit Sub
    End If
    '...
End Sub

XPL0

XPL0 cleans up after itself. Its DOS Protected Mode Interface (DPMI) releases extended memory (since DOS can't do it). It restores any system vectors that were altered, such as the divide-by-zero exception vector. It also restores changes made to the 8254 system timer chip (or its equivalent).

The value following 'exit' is optional. It's passed to DOS and can be used by a controlling batch file in an IF ERRORLEVEL statement, and thus change the commands the batch file executes.

if Problem then exit 1;