Path: news.ruhr-uni-bochum.de!news.uni-stuttgart.de!uniol!uni-erlangen.de!news.tu-chemnitz.de!irz401!fu-berlin.de!main.Germany.EU.net!EU.net!www.nntp.primenet.com!nntp.primenet.com!ddsw1!news.mcs.net!van-bc!unixg.ubc.ca!nntp.cs.ubc.ca!psgrain!nntp.teleport.com!usenet From: Brad_Appleton-GBDA001@email.mot.com Newsgroups: comp.lang.perl.announce,comp.lang.perl.misc Subject: ANNOUNCE: AtExit-1.02 now on CPAN Followup-To: comp.lang.perl.misc Date: 6 Sep 1996 20:54:15 GMT Organization: Motorola AIEG Northbrook Lines: 166 Approved: merlyn@stonehenge.com (comp.lang.perl.announce) Message-ID: <50q31n$f5q@nadine.teleport.com> Reply-To: Brad_Appleton-GBDA001@email.mot.com NNTP-Posting-Host: kelly.teleport.com Keywords: Perl5, atexit() X-Disclaimer: The "Approved" header verifies header information for article transmission and does not imply approval of content. Xref: news.ruhr-uni-bochum.de comp.lang.perl.announce:419 comp.lang.perl.misc:44494 Version 1.02 of my AtExit package is now available on CPAN as $CPAN/authors/id/BRADAPP/AtExit-1.02.tar.gz where $CPAN is the leading path to your nearest CPAN site. AtExit.pm is a very simple Perl5 module which provides a function named atexit() to perform standard C-style exit processing, and another function named rmexit() to remove functions registered with atexit(). The manpage for AtExit is included below my signature. If youre having trouble connecting to CPAN, let me know. The package is pretty small (about 430 lines of text, just over 16Kbytes). It shouldnt be much problem to email it. AtExit is free software; you can redistribute it and/or modify it under the same terms as Perl itself. ------------------------------------------------------------------------------ Brad_Appleton-GBDA001@email.mot.com Motorola AIEG, Northbrook, IL USA "And miles to go before I sleep." DISCLAIMER: I said it, not my employer! ------------------------------------------------------------------------------ NAME atexit -- Register a subroutine to be invoked at program-exit time. rmexit -- Unregister a subroutine that was registered with atexit. SYNOPSIS use AtExit; sub cleanup { my @args = @_; print "cleanup() executing: args = @args\n"; } $_ = atexit(\&cleanup, "This call was registered first"); print "first call to atexit() returned $_\n"; $_ = atexit("cleanup", "This call was registered second"); print "second call to atexit() returned $_\n"; $_ = atexit("cleanup", "This call should've been unregistered by rmexit"); rmexit($_) || warn "couldnt' unregister exit-sub $_!"; END { print "*** Now performing program-exit processing ***\n"; } DESCRIPTION The AtExit module provides ANSI-C style exit processing modeled after the `atexit()' function in the standard C library (see the atexit(3C) manpage). Various exit processing routines may be registered by calling `atexit()' and passing it the desired subroutine along with any desired arguments. Then, at program-exit time, the subroutines registered with `atexit()' are invoked with their given arguments in the *reverse* order of registration (last one registered is invoked first). Registering the same subroutine more than once will cause that subroutine to be invoked once for each registration. The `atexit()' function exported by AtExit should be passed a subroutine name or reference, optionally followed by the list of arguments with which to invoke it at program-exit time. Anonymous subroutine references passed to `atexit()' act as "closures" (which are described in the perlref manpage). If a subroutine *name* is specified (as opposed to a subroutine reference) then, unless the subroutine name has an explicit package prefix, it is assumed to be the name of a subroutine in the caller's current package. A reference to the specified subroutine is obtained, and, if invocation arguments were specified, it is "wrapped up" in a closure which invokes the subroutine with the specified arguments. The resulting subroutine reference is prepended to the front of the `@AtExit::EXIT_SUBS' list of exit-handling subroutines and the reference is then returned to the caller (just in case you might want to unregister it later using `rmexit()'). If the given subroutine could *not* be registered, then the value zero is returned. The `rmexit()' function exported by AtExit should be passed one or more subroutine references, each of which was returned by a previous call to `atexit()'. For each argument given, `rmexit()' will look for it in the `@AtExit::EXIT_SUBS' list of exit-handling subroutines and remove the first such match from the list. The value returned will be the number of subroutines that were successfully unregistered. At program-exit time, the `END{}' block in the AtExit module iterates over the subroutine references in the `@AtExit::EXIT_SUBS' array and invokes each one in turn (each subroutine is removed from the front of the queue immediately before it is invoked). Note that the subroutines in this queue are invoked in first-to-last order (the *reverse* order in which they were registered with `atexit()'). Invoking `atexit()' and `rmexit()' during program-exit The variable `$AtExit::IGNORE_WHEN_EXITING' specifies how calls to `atexit()' will be handled if they occur during the time that subroutines registered with `atexit()' are being invoked. By default, this variable is set to a non-zero value, which causes `atexit()' to *ignore* any calls made to it during this time (a value of zero will be returned). This behavior is consistent with that of the standard C library function of the same name. If desired however, the user may enable the registration of subroutines by `atexit()' during this time by setting `$AtExit::IGNORE_WHEN_EXITING' to zero or to the empty string. Just remember that any subroutines registered with `atexit()' during program-exit time will be placed at the *front* of the queue of yet-to- be-invoked exit-processing subroutines. Regardless of when it is invoked, `rmexit()' will *always* attempt to unregister the given subroutines (even when called during program-exit processing). Keep in mind however that if it is invoked during program- exit processing then it will *fail* to unregister any exit-processing subroutines that have *already been invoked* by the `END{}' block in the AtExit module (since those subroutine calls have already been removed from the `@AtExit::EXIT_SUBS' list). The variable `$AtExit::EXITING' may be examined to determine if routines registered using `atexit()' are currently in the process of being invoked. It will be non-zero if they are and zero otherwise. NOTES The usual Perl way of doing exit processing is through the use of `END{}' blocks (see the section on "Package Constructors and Destructors" in the perlmod manpage). The AtExit module implements its exit processing with an `END{}' block that invokes all the subroutines registered by `atexit()' in the array `@AtExit::EXIT_SUBS'. If any other `END{}' block processing is specified in the user's code or in any other packages it uses, then the order in which the exit processing takes place is subject to Perl's rules for the order in which `END{}' blocks are processed. This may affect when subroutines registered with `atexit()' are invoked with respect to other exit processing that is to be performed. In particular, if `atexit()' is invoked from within an `END{}' block that executes *after* the `END{}' block in the AtExit module, then the corresponding subroutine that was registered will never be invoked by the AtExit module's exit-processing code. `END{}' block processing order `END{}' blocks, including those in other packages, get called in the reverse order in which they appear in the code. (`atexit()' subroutines get called in the reverse order in which they are registered.) If a package gets read via "use", it will act as if the `END{}' block was defined at that particular part of the "main" code. Packages read via "require" will be executed after the code of "main" has been parsed and will be seen last so will execute first (they get executed in the context of the package in which they exist). It is important to note that `END{}' blocks only get called on normal termination (which includes calls to `die()' or `Carp::croak()'). They do *not* get called when the program terminates *abnormally* (due to a signal for example) unless special arrangements have been made by the programmer (e.g. using a signal handler -- see the section on "%SIG{expr}" in the perlvar manpage). SEE ALSO the atexit(3C) manpage describes the `atexit()' function for the standard C library (the actual Unix manual section in which it appears may differ from platform to platform - try sections 3C, 3, 2C, and 2). Further information on anonymous subroutines ("closures") may be found in the perlref manpage. For more information on `END{}' blocks, see the section on "Package Constructors and Destructors" in the perlmod manpage. See the section on "%SIG{expr}" in the perlvar manpage for handling abnormal program termination. AUTHOR Andrew Langmead (initial draft). Brad Appleton (final version). .