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Is there exception handling in AIX/Unix/Linux similar to how exceptions
are handled in C++? I have a unix programming book by Stevens and a
couple of Perl books just arrived and I dont see any mention of
throwing and catching exceptions. ( I just read about die, the non zero
return value standard and stderr )

An example might be a socket connection to a remote system. I always
want that connection to shutdown in a way the remote system expects.
Will a Perl script be able to catch all the potential dieing that could
happen in the process and send a nice disconnect message to the remote
system?

thanks,

-Steve

StephenRichter@gmail.com writes:

> Is there exception handling in AIX/Unix/Linux similar to how exceptions
> are handled in C++?

In what language? Yes, in C++.

> I have a unix programming book by Stevens and a
> couple of Perl books just arrived and I dont see any mention of
> throwing and catching exceptions.

Stevens book is all in C, and there is no structured exception
handling in that language.

> ( I just read about die, the non zero
> return value standard and stderr )

In Perl, you could 'catch' exceptions like this:

eval "some code which might die";
if ($@) { # did die ...

> An example might be a socket connection to a remote system. I always
> want that connection to shutdown in a way the remote system expects.
> Will a Perl script be able to catch all the potential dieing that could
> happen in the process and send a nice disconnect message to the remote
> system?

Sure.

However, if remote requires a nice disconnect, it is broken: think
what would happen if you cut the network cable from local host
(while the app is running), then reboot it and plug it back in.

Cheers,
--
In order to understand recursion you must first understand recursion.
Remove /-nsp/ for email.

Paul Pluzhnikov wrote:
> StephenRichter@gmail.com writes:
>
> > Is there exception handling in AIX/Unix/Linux similar to how exceptions
> > are handled in C++?
>
> In what language? Yes, in C++.
>
> > I have a unix programming book by Stevens and a
> > couple of Perl books just arrived and I dont see any mention of
> > throwing and catching exceptions.
>
> Stevens book is all in C, and there is no structured exception
> handling in that language.

Does Unix itself have a call stack and a facility for unwinding that
stack when an exception is thrown? Windows for example uses structured
exception handling that embeds exception handling entries in the call
stack of a thread. On the system I am migrating from, the as400, an
exception is thrown by sending an *escape message from one level of the
call stack to a prior level.

-Steve

StephenRichter@gmail.com writes:

> Does Unix itself have

There is no such thing as "UNIX itself".

There are Linux Fedora Core 2, Red Hat Enterprise Server 4.0,
Solaris 10 update 1, AIX 5.3, etc. etc.

> a call stack

Every computer that is capable of running UNIX has a "call stack".
Some processors have special "call stack" instructions, others
"emulate" it, using "regular" registers and "normal" load/store
instructions, etc.

> and a facility for unwinding that
> stack when an exception is thrown?

What does "when exception is thrown" mean in a language that doesn't
support exceptions (such as C)?

Some system libraries (e.g. glibc on x86) support unwinding stack,
provided the code has not been compiled in a way making such
unwinding impossible (e.g. 'gcc -O3 -fomit-frame-pointer ...').

> Windows for example uses structured
> exception handling that embeds exception handling entries in the call
> stack of a thread.

"Windows" doesn't do that. One particular compiler: "MicroSoft Visual C"
has an extension which allows programmer to easily embed such entries.

Windows also has a system library (KERNEL32.DLL IIRC) which knows
how to find such entries, and how to "do the right thing" when an
exception is thrown by KERNEL32.DLL RaiseException() call.

> On the system I am migrating from, the as400,

I've never worked on one of these, and claim absolute zero knowledge.

> exception is thrown by sending an *escape message from one level of the
> call stack to a prior level.

There are languages (C++, Perl, Python, etc.) that support this
concept, and there are library implementations which allow one to
unwind call stack, but there is no "general exception facility"
on UNIX that's applicable to all UNIXes and all languages.

Cheers,
--
In order to understand recursion you must first understand recursion.
Remove /-nsp/ for email.