Exception handling syntax varies between programming languages to accommodate their overall syntax. Some languages don't call the concept exception handling or they may not have direct facilities for it, but they can still provide means for implementing it. A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. ... For other uses, see Syntax (disambiguation). ... Exception handling is a programming language construct or computer hardware mechanism designed to handle the occurrence of some condition that changes the normal flow of execution. ...

Catalogue of exception handling syntaxes

Ada

 with Ada.Exceptions; use Ada.Exceptions; procedure Foo is begin Do_Something_Interesting; -- Start of exception declaration exception when Constraint_Error => -- Handle constraint error when Storage_Error => -- Propagate the Storage_Error as different exception with some useful message raise Some_Error with "Out of memory"; when Error : others => -- Handle all others Put ("Exception: "); Put_Line (Exception_Name (Error)); Put (Exception_Message (Error)); end Foo; 

For a more complete discussion of exceptions in Ada see the wikibook on Ada. Ada is a structured, statically typed imperative computer programming language designed by a team led by Jean Ichbiah of CII Honeywell Bull under contract by the US Navy during 1977–1983. ...

BASIC

 ON ERROR GOTO handler OPEN "Somefile.txt" FOR INPUT AS #1 CLOSE #1 PRINT "File opened successfully" END 

 handler: PRINT "File does not exist" END 

Screenshot of Atari BASIC, an early BASIC language for small computers. ...

C#

 public static void Main() { try { // Code that could throw an exception } catch(System.Net.WebException exp) { //Process a WebException } catch(System.Exception) { //Process a System level CLR exception, that is not a System.Net.WebException //since the exception has not been given an identifier it cannot be referenced } catch { //Process a non-CLR exception } finally { // (optional) code that will *always* execute } } 

The title given to this article is incorrect due to technical limitations. ...

C++

 #include <exception> int main() { try { // do something (might throw an exception) } catch (const std::exception& e) { // handle exception e } catch (...) { // unknown exception, should not happen } } 

In C++, a resource acquisition is initialization technique can be used to clean up resources in exceptional situations. C++ (IPA pronounciation: ) is a general-purpose, high-level programming language with low-level facilities. ... Resource Acquisition Is Initialization, often referred to by the acronym RAII, is a popular programming technique in C++ and D. The technique combines acquisition and release of resources with initialization and uninitialization of variables. ...

D

 import std.stdio; // for writefln() int main() { try { // do something that might throw an exception } catch (FooException e) { // handle exceptions of type FooException } catch (Object o) { // handle any other exceptions writefln("Unhandled exception: ", o); return 1; } return 0; } 

In D, a finally clause or the resource acquisition is initialization technique can be used to clean up resources in exceptional situations. D is an object-oriented, imperative system programming language designed by Walter Bright of Digital Mars as a re-engineering of C/C++. He has done this by re-designing many C++ features, and borrowing ideas from other programming languages. ... Resource Acquisition Is Initialization, often referred to by the acronym RAII, is a popular programming technique in C++ and D. The technique combines acquisition and release of resources with initialization and uninitialization of variables. ...

Java

 try { // Normal execution path } catch (ExampleException ee) { // deal with the ExampleException } finally { // This optional section is executed upon termination of any of the try or catch blocks above } 

Java is an object-oriented programming language developed by Sun Microsystems in the early 1990s. ...

Ruby

 begin # Do something nifty raise SomeError, "This is the error message!" # Uh-oh! rescue SomeError # This is executed when a SomeError exception # is raised rescue AnotherError => error # Here, the exception object is referenced from the # `error' variable else # This is executed only if no exceptions were raised ensure # This is always executed, exception or not end 

Ruby is a reflective, object-oriented programming language. ...

Python

 try: f = file("aFileName") except IOError: print "Unable to open file" except: # catch all exceptions print "Unexpected error" else: # no exception was raised try: f.write(could_make_error()) finally: # clean-up actions f.close() 

Python is a programming language created by Guido van Rossum in 1990. ...

OCaml

 exception MyException of string * int (* exceptions can carry a value *) let _ = try raise (MyException ("not enough food", 2)); print_endline "Not reached" with | MyException (s, i) -> Printf.printf "MyException: %s, %dn" s i | _ -> (* catch all exceptions *) print_endline "Unexpected exception" 

Objective Caml (OCaml) is the main implementation of the Caml programming language, created by Xavier Leroy, Jérôme Vouillon, Damien Doligez, Didier Rémy and others in 1996. ...

C

The most common way to implement exception handling in standard C is to use setjmp/longjmp functions: Wikibooks has a book on the topic of C Programming The C programming language (often, just C) is a general-purpose, procedural, imperative computer programming language developed in the early 1970s by Dennis Ritchie for use on the Unix operating system. ... The source is licensed under the GFDL, but has large invariant sections and cover texts. ...

 #include <setjmp.h> #include <stdio.h> enum { SOME_EXCEPTION = 1 }; jmp_buf state; int main() { int exception; if((exception = setjmp(state)) == 0) // try { if(/* something happened */) longjmp(state, SOME_EXCEPTION); // throw SOME_EXCEPTION } else switch(exception) { case SOME_EXCEPTION: // catch SOME_EXCEPTION puts("SOME_EXCEPTION caught"); break; default: // catch ... puts("Some strange exception"); } return 0; } 

Some operating systems also have similar features, for example Microsoft Windows has "Structured Exception Handling" (SEH): An operating system (OS) is a computer program that manages the hardware and software resources of a computer. ... Microsoft Windows is the name of several families of proprietary operating systems by Microsoft. ... It has been suggested that Trap (computing) be merged into this article or section. ...

 int filterExpression (EXCEPTION_POINTERS* ep) { ++ep->ContextRecord->Eip; return EXCEPTION_CONTINUE_EXECUTION; } int main() { static int zero; __try { zero = 1/zero; printf ("Past the exception.n"); } __except (filterExpression (GetExceptionInformation())) { printf ("Handler called.n"); } return 0; } 

• see also Vector Exception Handling (VEH).

Perl

 eval { # Code that could throw an exception } if($@){ # Handle exception here. (The exception object is in $@) } 

Perl is a dynamic programming language created by Larry Wall and first released in 1987. ...

PHP

 // Exception handling is only available in PHP versions 5 and greater. == try == try { ... // Code which might throw an exception } catch (FirstExceptionClass $exception) { ... // Code which handles this exception } catch (SecondExceptionClass $exception) { // you get the idea what i mean ;) } 

(php5powerprogramming: ISBN 0-13-147149-X, page 77) PHP (PHP: Hypertext Preprocessor) is a reflective programming language originally designed for producing dynamic Web pages. ...

Delphi

 try try // Code which may raise an exception except on E:Exception do // Code to call when an exception is raised end; finally // Code which will be executed whether or not an exception is raised (e.g. clean-up code) end; 

Delphi is the primary programming language of Borland Delphi. ...

Fault Tolerant Shell

 try for 30 minutes cd /tmp rm -f data forany host in xxx yyy zzz wget http://${host}/fresh.data data end end 

The Fault-Tolerant Shell (ftsh) is a small language for system integration that makes failures a first class concept. ...

See also

• Exception handling for the semantics of exception handling
• Syntax for definition of syntax in computer science