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SPLAIN !!!SPLAIN NAME SYNOPSIS DESCRIPTION EXAMPLES INTERNALS BUGS AUTHOR ---- !!NAME diagnostics - Perl compiler pragma to force verbose warning diagnostics splain - standalone program to do the same thing !!SYNOPSIS As a pragma: use diagnostics; use diagnostics -verbose; enable diagnostics; disable diagnostics; Aa a program: perl program 2 !!DESCRIPTION __The__ diagnostics __Pragma__ This module extends the terse diagnostics normally emitted by both the perl compiler and the perl interpreter, augmenting them with the more explicative and endearing descriptions found in perldiag. Like the other pragmata, it affects the compilation phase of your program rather than merely the execution phase. To use in your program as a pragma, merely invoke use diagnostics; at the start (or near the start) of your program. (Note that this ''does'' enable perl's __-w__ flag.) Your whole compilation will then be subject(ed :-) to the enhanced diagnostics. These still go out __STDERR__ . Due to the interaction between runtime and compiletime issues, and because it's probably not a very good idea anyway, you may not use no diagnostics to turn them off at compiletime. However, you may control their behaviour at runtime using the ''disable()'' and ''enable()'' methods to turn them off and on respectively. The __-verbose__ flag first prints out the perldiag introduction before any other diagnostics. The $diagnostics::PRETTY variable can generate nicer escape sequences for pagers. Warnings dispatched from perl itself (or more accurately, those that match descriptions found in perldiag) are only displayed once (no duplicate descriptions). User code generated warnings ala ''warn()'' are unaffected, allowing duplicate user messages to be displayed. __The__ ''splain'' __Program__ While apparently a whole nuther program, ''splain'' is actually nothing more than a link to the (executable) ''diagnostics.pm'' module, as well as a link to the ''diagnostics.pod'' documentation. The __-v__ flag is like the use diagnostics -verbose directive. The __-p__ flag is like the $diagnostics::PRETTY variable. Since you're post-processing with ''splain'', there's no sense in being able to ''enable()'' or ''disable()'' processing. Output from ''splain'' is directed to __STDOUT__ , unlike the pragma. !!EXAMPLES The following file is certain to trigger a few errors at both runtime and compiletime: use diagnostics; print NOWHERE If you prefer to run your program first and look at its problem afterwards, do this: perl -w test.pl 2 Note that this is not in general possible in shells of more dubious heritage, as the theoretical (perl -w test.pl Because you just moved the existing __stdout__ to somewhere else. If you don't want to modify your source code, but still have on-the-fly warnings, do this: exec 3 Nifty, eh? If you want to control warnings on the fly, do something like this. Make sure you do the use first, or you won't be able to get at the ''enable()'' or ''disable()'' methods. use diagnostics; # checks entire compilation phase print disable diagnostics; # only turns off runtime warnings print enable diagnostics; # turns back on runtime warnings print disable diagnostics; print !!INTERNALS Diagnostic messages derive from the ''perldiag.pod'' file when available at runtime. Otherwise, they may be embedded in the file itself when the splain package is built. See the ''Makefile'' for details. If an extant $SIG{__WARN__} handler is discovered, it will continue to be honored, but only after the ''diagnostics::splainthis()'' function (the module's $SIG{__WARN__} interceptor) has had its way with your warnings. There is a $diagnostics::DEBUG variable you may set if you're desperately curious what sorts of things are being intercepted. BEGIN { $diagnostics::DEBUG = 1 } !!BUGS Not being able to say ``no diagnostics'' is annoying, but may not be insurmountable. The -pretty directive is called too late to affect matters. You have to do this instead, and ''before'' you load the module. BEGIN { $diagnostics::PRETTY = 1 } I could start up faster by delaying compilation until it should be needed, but this gets a ``panic: top_level'' when using the pragma form in Perl 5.001e. While it's true that this documentation is somewhat subserious, if you use a program named ''splain'', you should expect a bit of whimsy. !!AUTHOR Tom Christiansen tchrist@mox.perl.com'' '' ----
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