table of contents
Log::Report(3pm) | User Contributed Perl Documentation | Log::Report(3pm) |
NAME¶
Log::Report - report a problem, with exceptions and translation supportINHERITANCE¶
Log::Report is a Exporter
SYNOPSIS¶
# Invocation with 'mode' to get trace and verbose messages use Log::Report mode => 'DEBUG'; # Usually invoked with a domain, which groups packages use Log::Report 'my-domain', %options; # Interpolation syntax via String::Print # First step to translations, once you need it. print __x"my name is {name}", name => $n; # print, so no exception print __"Hello World\n"; # (optional) translation, no interpolation print __x'Hello World'; # SYNTAX ERROR!! ' is alternative for :: # Functions replacing die/warn/carp, casting exceptions. error "oops"; # exception like die(), no translation -f $config or panic "Help!"; # alert/error/fault/info/...more # Combined exception, interpolation, and optional translation error __x"Help!"; # __x() creates ::Message object error __x('gettext msgid', param => $value, ...) if $condition; # Also non fatal "exceptions" find their way to dispatchers info __x"started {pid}", pid => $$; # translatable debug "$i was here!"; # you probably do not want to translate debug panic "arrghhh"; # like Carp::Confess # Many destinations for an exception message (may exist in parallel) dispatcher PERL => 'default' # see Log::Report::Dispatcher: use die/warn , reasons => 'NOTICE-'; # this dispatcher is already present at start dispatcher SYSLOG => 'syslog'# also send to syslog , charset => 'iso-8859-1' # explicit character conversions , locale => 'en_US'; # overrule user's locale dispatcher close => 'default'; # stop default die/warn dispatcher # Fill-in values, like Locale::TextDomain and gettext # See Log::Report::Message section DETAILS fault __x"cannot allocate {size} bytes", size => $size; fault "cannot allocate $size bytes"; # no translation, ok fault __x"cannot allocate $size bytes"; # not translatable, wrong # Translation depending on count # Leading and trailing whitespace stay magically outside translation # tables. @files in scalar context. Special parameter with _ print __xn"found one file\n", "found {_count} files", @files; # Borrow from an other text-domain (see Log::Report::Message) print __x(+"errors in {line}", _domain => 'global', line => $line); # catch errors (implements hidden eval/die) try { error }; if($@) {...} # $@ isa Log::Report::Dispatcher::Try if(my $exception = $@->wasFatal) # ::Exception object # Language translations at the output component # Translation management via Log::Report::Lexicon use POSIX::1003::Locale qw/setlocale LC_ALL/; setlocale(LC_ALL, 'nl_NL'); info __"Hello World!"; # in Dutch, if translation table found # Exception classes, see Log::Report::Exception try { error __x"something", _class => 'parsing,schema' }; if($@->wasFatal->inClass('parsing')) ...
DESCRIPTION¶
Handling messages directed to users can be a hassle, certainly when the same software is used for command-line and in a graphical interfaces (you may not now how it is used, writing an abstract module), or has to cope with internationalization; this modules tries to simplify this. "Log::Report" combines- . exceptions (like error and info), with
- . logging (like Log::Log4Perl and syslog), and
- . translations (like "gettext" and Locale::TextDomain)
FUNCTIONS¶
Report Production and Configuration¶
- dispatcher( <$type, $name, %options>|<$command, @names> )
- The "dispatcher" function controls access to dispatchers: the
back-ends which process messages, do the logging. Dispatchers are global
entities, addressed by a symbolic $name. Please read
Log::Report::Dispatcher as well.
The "Log::Report" suite has its own dispatcher TYPES, but also
connects to external dispatching frameworks. Each need some (minor)
conversions, especially with respect to translation of REASONS of the
reports into log-levels as the back-end understands.
The %options are a mixture of parameters needed for the Log::Report
dispatcher wrapper and the settings of the back-end. See
Log::Report::Dispatcher, the documentation for the back-end specific
wrappers, and the back-ends for more details.
Implemented COMMANDs are "close", "find",
"list", "disable", "enable",
"mode", "filter", and "needs". Most commands
are followed by a LIST of dispatcher @names to be addressed. For
"mode" see section "Run modes"; it requires a MODE
argument before the LIST of NAMEs. Non-existing names will be ignored.
When "ALL" is specified, then all existing dispatchers will get
addressed. For "filter" see "Filters" in
Log::Report::Dispatcher; it requires a CODE reference before the @names of
the dispatchers which will have the it applied (defaults to all).
With "needs", you only provide a REASON: it will return the list
of dispatchers which need to be called in case of a message with the
REASON is triggered.
For both the creation as COMMANDs version of this method, all objects
involved are returned as LIST, non-existing ones skipped. In SCALAR
context with only one name, the one object is returned.
example: play with dispatchers
dispatcher Log::Dispatcher::File => mylog => , accept => 'MISTAKE-' # for wrapper , locale => 'pt_BR' # other language , filename => 'logfile'; # for back-end dispatcher close => 'mylog'; # cleanup my $obj = dispatcher find => 'mylog'; my @obj = dispatcher 'list'; dispatcher disable => 'syslog'; dispatcher enable => 'mylog', 'syslog'; # more at a time dispatcher mode => 'DEBUG', 'mylog'; dispatcher mode => 'DEBUG', 'ALL'; my @need_info = dispatcher needs => 'INFO'; if(dispatcher needs => 'INFO') ... # anyone needs INFO # Getopt::Long integration: see Log::Report::Dispatcher::mode() dispatcher PERL => 'default', mode => 'DEBUG', accept => 'ALL' if $debug;
- report( [%options], $reason, $message|<STRING,$params>, )
- The "report" function is sending (for some $reason) a $message
to be displayed or logged (by a `dispatcher'). This function is the core
for error(), info() etc functions, which are nicer names for
this exception throwing: better use those short names.
The $reason is a string like 'ERROR' (for function "error()"). The
$message is a Log::Report::Message object (which are created with the
special translation syntax like _ _x()). The $message may also be a
plain string, or an Log::Report::Exception object. The optional first
parameter is a HASH which can be used to influence the dispatchers.
The optional %options are listed below. Quite differently from other
functions and methods, they have to be passed in a HASH as first
parameter.
This function returns the LIST of dispatchers which accepted the $message.
When empty, no back-end has accepted it so the $message was
"lost". Even when no back-end needs the message, the program
will still exit when there is a $reason to "die()".
-Option --Default errno $! or 1 is_fatal <depends on reason> locale undef location undef stack undef to undef
- errno => INTEGER
- When the $reason includes the error text (See "Run modes"), you can overrule the error code kept in $!. In other cases, the return code defaults to 1 (historical UNIX behavior). When the message $reason (combined with the run-mode) is severe enough to stop the program, this value as return code of the program. The use of this option itself will not trigger an "die()".
- is_fatal => BOOLEAN
- Some logged exceptions are fatal, other aren't. The default usually is correct. However, you may want an error to be caught (usually with try()), redispatch it to syslog, but without it killing the main program.
- locale => LOCALE
- Use this specific locale, in stead of the user's preference.
- location => STRING
- When defined, this location is used in the display. Otherwise, it is determined automatically if needed. An empty string will disable any attempt to display this line.
- stack => ARRAY
- When defined, that data is used to display the call stack. Otherwise, it is collected via "caller()" if needed.
- to => NAME|ARRAY-of-NAMEs
- Sent the $message only to the NAMEd dispatchers. Ignore unknown NAMEs. Still, the dispatcher needs to be enabled and accept the REASONs.
example: for use of report()
# long syntax example report TRACE => "start processing now"; report INFO => '500: ' . __'Internal Server Error'; # explicit dispatcher, no translation report {to => 'syslog'}, NOTICE => "started process $$"; notice "started process $$", _to => 'syslog'; # same # short syntax examples trace "start processing now"; warning __x'Disk {percent%.2f}% full', percent => $p if $p > 97; # error message, overruled to be printed in Brazilian report {locale => 'pt_BR'} , WARNING => "do this at home!";
- try(CODE, %options)
- Execute the CODE while blocking all dispatchers as long as it is running.
The exceptions which occur while running the CODE are caught until it has
finished. When there where no fatal errors, the result of the CODE
execution is returned.
After the CODE was tried, the $@ will contain a Log::Report::Dispatcher::Try
object, which contains the collected messages.
Run-time errors from Perl and die's, croak's and confess's within the
program (which shouldn't appear, but you never know) are collected into an
Log::Report::Message object, using Log::Report::Die.
The %options are passed to the constructor of the try-dispatcher, see
Log::Report::Dispatcher::Try::new(). For instance, you may like to
add "mode => 'DEBUG'", or "accept => 'ERROR-'".
Be warned that the parameter to "try" is a CODE reference.
This means that you shall not use a comma after the block when there are
%options specified. On the other hand, you shall use a semi-colon after
the block if there are no arguments.
Be warned that the {} are interpreted as subroutine, which means
that, for instance, it has its own @_. The manual-page of Try::Tiny lists
a few more side-effects of this.
example:
my $x = try { 3/$x }; # mind the ';' !! if($@) { # signals something went wrong if(try {...}) { # block ended normally, returns bool try { ... } # no comma!! mode => 'DEBUG', accept => 'ERROR-'; try sub { ... }, # with comma, also \&function mode => 'DEBUG', accept => 'ALL'; my $response = try { $ua->request($request) }; if(my $e = $@->wasFatal) ...
Abbreviations for report()¶
The following functions are all wrappers for calls to report(), and available when "syntax is SHORT" (by default, see import()). You cannot specify additional options to influence the behavior of "report()", which are usually not needed anyway.- alert($message)
- Short for "report ALERT => $message"
- assert($message)
- Short for "report ASSERT => $message"
- error($message)
- Short for "report ERROR => $message"
- failure($message)
- Short for "report FAILURE => $message"
- fault($message)
- Short for "report FAULT => $message"
- info($message)
- Short for "report INFO => $message"
- mistake($message)
- Short for "report MISTAKE => $message"
- notice($message)
- Short for "report NOTICE => $message"
- panic($message)
- Short for "report PANIC => $message"
- trace($message)
- Short for "report TRACE => $message"
- warning($message)
- Short for "report WARNING => $message"
Language Translations¶
The language translations are initiate by limited set of functions which contain two under-scores ("__") in their name. Most of them return a Log::Report::Message object. Be warned(1) that -in general- its considered very bad practice to combine multiple translations into one message: translating may also affect the order of the translated components. Besides, when the person which translates only sees smaller parts of the text, his (or her) job becomes more complex. So:print __"Hello" . ', ' . __"World!"; # works, but to be avoided print __"Hello, World!"; # preferred, complete sentenceThe the former case, tricks with overloading used by the Log::Report::Message objects will still make delayed translations work. In normal situations, it is not a problem to translate interpolated values:
print __"the color is {c}", c => __"red";Be warned(2) that using "__'Hello'" will produce a syntax error like "String found where operator expected at .... Can't find string terminator "'" anywhere before EOF". The first quote is the cause of the complaint, but the second generates the error. In the early days of Perl, the single quote was used to separate package name from function name, a role which was later replaced by a double-colon. So "__'Hello'" gets interpreted as "__::Hello '". Then, there is a trailing single quote which has no counterpart.
- N__($msgid)
- Label to indicate that the string is a text which will be translated
later. The function itself does nothing. See also N_ _w().
This no-op function is used as label to the xgettext program to build the
translation tables.
example: how to use N__()
# add three msgids to the translation table my @colors = (N__"red", N__"green", N__"blue"); my @colors = N__w "red green blue"; # same print __ $colors[1]; # translate green # using __(), would work as well my @colors = (__"red", __"green", __"blue"); print $colors[1]; # however: this will always create all Log::Report::Message objects, # where maybe only one is used.
- N__n($single_msgid, $plural_msgid)
- Label to indicate that the two MSGIDs are related, the first as single,
the seconds as its plural. Only used to find the text fragments to be
translated. The function itself does nothing.
example: how to use N_ _n()
my @save = N__n "save file", "save files"; my @save = (N__n "save file", "save files"); my @save = N__n("save file", "save files"); # be warned about SCALARs in prototype! print __n @save, $nr_files; # wrong! print __n $save[0], $save[1], @files, %vars;
- N__w(STRING)
- This extension to the Locale::TextDomain syntax, is a combined
"qw" (list of quoted words) and N__() into a list of
translatable words.
example: of N_ _w()
my @colors = (N__"red", N__"green", N__"blue"); my @colors = N__w"red green blue"; # same print __ $colors[1];
- __($msgid)
- This function (name is two under-score characters) will cause the
$msgid to be replaced by the translations when doing the actual output.
Returned is a Log::Report::Message object, which will be used in
translation later. Translating is invoked when the object gets
stringified. When you have no translation tables, the $msgid will be shown
untranslated.
If you need options for Log::Report::Message::new() then use
__x(); the prototype of this function does not permit parameters:
it is a prefix operator!
example: how to use __()
print __"Hello World"; # translated into user's language print __'Hello World'; # syntax error! print __('Hello World'); # ok, translated print __"Hello", " World"; # World not translated my $s = __"Hello World"; # creates object, not yet translated print ref $s; # Log::Report::Message print $s; # ok, translated print $s->toString('fr'); # ok, forced into French
- __n($msgid, $plural_msgid, $count, PAIRS)
- It depends on the value of $count (and the selected language) which text
will be displayed. When translations can not be performed, then $msgid
will be used when $count is 1, and PLURAL_MSGSID in other cases. However,
some languages have more complex schemes than English.
The PAIRS are options for Log::Report::Message::new() and variables
to be filled in.
example: how to use _ _n()
print __n "one", "more", $a; print __n("one", "more", $a), "\n"; print +(__n "one", "more", $a), "\n"; # new-lines are ignore at lookup, but printed. print __n "one\n", "more\n", $a; # count is in scalar context # the value is also available as _count print __n "found one\n", "found {_count}\n", @r; # ARRAYs and HASHes are counted print __n "one", "more", \@r;
- __nx($msgid, $plural_msgid, $count, PAIRS)
- It depends on the value of $count (and the selected language) which text
will be displayed. See details in _ _n(). After translation, the
VARIABLES will be filled-in.
The PAIRS are options for Log::Report::Message::new() and variables
to be filled in.
example: how to use _ _nx()
print __nx "one file", "{_count} files", $nr_files; print __nx "one file", "{_count} files", @files; local $" = ', '; print __nx "one file: {f}", "{_count} files: {f}", @files, f => \@files;
- __x($msgid, PAIRS)
- Translate the $msgid and then interpolate the VARIABLES in that string. Of course, translation and interpolation is delayed as long as possible. Both OPTIONS and VARIABLES are key-value pairs. The PAIRS are options for Log::Report::Message::new() and variables to be filled in.
- __xn($single_msgid, $plural_msgid, $count, $paurs)
- Same as __nx(), because we have no preferred order for 'x' and 'n'.
Configuration¶
- $obj->import( [$level,][$domain,] %options )
- The import is automatically called when the package is compiled. For all
packages but one in your distribution, it will only contain the name of
the $domain.
For one package, the import list may additionally contain textdomain
configuration %options. These %options are used for all packages which use
the same $domain. These are alternatives:
use Log::Report 'my-domain', %config, %domain_config; use Log::Report 'my-domain', %config; textdomain 'my-domain', %domain_config;
The latter syntax has major advantages, when the configuration of the domain is determined at run-time. It is probably also easier to understand. See Log::Report::Domain::configure(), for the list of %options for the domain configuration. Here, we only list the options which are related to the normal import behavior. The export $level is a plus (+) followed by a number, for instance +1, to indicate to on which caller level we need to work. This is used in Log::Report::Optional. It defaults to '0': my direct caller.-Option--Default import undef mode 'NORMAL' syntax 'SHORT'
- import => FUNCTION|ARRAY
- [0.998] When not specified, the "syntax" option determines the list of functions which are being exported. With this option, the "syntax" option is ignored and only the specified FUNCTION(s) are imported.
- mode => LEVEL
- This sets the default mode for all created dispatchers. You can also
selectively change the output mode, like
dispatcher PERL => 'default', mode => 3
- syntax => 'REPORT'|'SHORT'|'LONG'
- The SHORT syntax will add the report abbreviations (like function error()) to your name-space. Otherwise, each message must be produced with report(). "LONG" is an alternative to "REPORT": both do not polute your namespace with the useful abbrev functions.
example: of import
use Log::Report mode => 3; # '3' or 'DEBUG' use Log::Report 'my-domain'; # in each package producing messages use Log::Report 'my-domain' # in one package, top of distr , mode => 'VERBOSE' , syntax => 'REPORT' # report ERROR, not error() , translator => Log::Report::Translator::POT->new ( lexicon => '/home/mine/locale' # bindtextdomain , charset => 'UTF-8' # codeset ) , native_language => 'nl_NL'; # untranslated msgs are Dutch use Log::Report import => 'try'; # or ARRAY of functions
- textdomain( <[$domain], $config> | <$domain, 'DELETE'> )
- [1.00] Without CONFIGuration, this returns the Log::Report::Domain object which administers the $domain, by default the domain effictive in the scope of the package. A very special case is for "DELETE", which will remove the domain configuration.
Reasons¶
- Log::Report->needs( $reason, [$reasons] )
- Returns true when the reporter needs any of the $reasons, when any of the
active dispatchers is collecting messages in the specified level. This is
useful when the processing of data for the message is relatively
expensive, but for instance only required in debug mode.
example:
if(Log::Report->needs('TRACE')) { my @args = ...expensive calculation...; trace "your options are: @args"; }
DETAILS¶
Introduction¶
There are three steps in this story: produce some text on a certain condition, translate it to the proper language, and deliver it in some way to a user. Texts in Perl are produced by commands like "print", "die", "warn", "carp", or "croak", which have no way of configuring the way they deliver text to the user. Therefore, they are replaced with a single new command: "report" with many abbreviations. Besides, the "print"/"warn"/"die" together produce only three different output levels with a message. Many people manually implement their own additional levels, like verbose and debug. Syslog has some extra levels as well, like "critical". The $reason argument to "report()" offers them all. The (optional) translations use the beautiful syntax defined by Locale::TextDomain, with some extensions (of course). The main difference is that the actual translations are delayed till the delivery step: until a dispatcher actually writes this message into a file or sends it to syslog. This means that the pop-up in the graphical interface of the user may show the text in the language of the user --say Chinese in utf8--, but at the same time syslog may write the latin1 English version of the same message.Background ideas¶
The following ideas are the base of this implementation:- . simplification
- Handling errors and warnings is probably the most labor-intensive task for a programmer: when programs are written correctly, up-to three-quarters of the code is related to testing, reporting, and handling (problem) conditions. Simplifying the way to create reports, simplifies programming and maintenance.
- . multiple dispatchers
- It is not the location where the (for instance) error occurs which determines what will happen with the text, but the main application which uses the the complaining module has control. Messages have a reason. Based on the `reason' classification, they can get ignored, send to one or multiple dispatchers, like Log::Dispatch, Log::Log4perl, or UNIX syslog.
- . delayed translations
- The background ideas are that of Locale::TextDomain, based on "gettext()". However, in the "Log::Report" infrastructure, translations are postponed until the text is dispatched to a screen or log-file; the same report can be sent to syslog in (for instance) English and to the user interface in Dutch.
Error handling models¶
There are two approaches to handling errors and warnings. In the first approach, as produced by "die", "warn" and the "carp" family of commands, the program handles the problem immediately on the location where the problem appears. In the second approach, an exception is thrown on the spot where the problem is created, and then somewhere else in the program the condition is handled. The implementation of exceptions in Perl5 is done with a eval-die pair: on the spot where the problem occurs, "die" is called. But, because of the execution of that routine is placed within an "eval", the program as a whole will not die, just the execution of a part of the program will seize. However, what if the condition which caused the routine to die is solvable on a higher level? Or what if the user of the code doesn't bother that a part fails, because it has implemented alternatives for that situation? Exception handling is quite clumsy in Perl5. The "Log::Report" set of distributions let modules concentrate on the program flow, and let the main program decide on the report handling model. The infrastructure to translate messages into multiple languages, whether to create exceptions or carp/die, to collect longer explanations with the messages, to log to mail or syslog, and so on, is decided in pluggable back-ends. The Reason for the report Traditionally, perl has a very simple view on error reports: you either have a warning or an error. However, it would be much clearer for user's and module-using applications, when a distinction is made between various causes. For instance, a configuration error is quite different from a disk-full situation. In "Log::Report", the produced reports in the code tell what is wrong. The main application defines loggers, which interpret the cause into (syslog) levels. Defined by "Log::Report" are- . trace (debug, program)
- The message will be used when some logger has debugging enabled. The messages show steps taken by the program, which are of interest by the developers and maintainers of the code, but not for end-users.
- . assert (program)
- Shows an unexpected condition, but continues to run. When you want the program to abort in such situation, that use "panic".
- . info (verbose, program)
- These messages show larger steps in the execution of the program. Experienced users of the program usually do not want to see all these intermediate steps. Most programs will display info messages (and higher) when some "verbose" flag is given on the command-line.
- . notice (program)
- An user may need to be aware of the program's accidental smart behavior, for instance, that it initializes a lasting "Desktop" directory in your home directory. Notices should be sparse.
- . warning (program)
- The program encountered some problems, but was able to work around it by smart behavior. For instance, the program does not understand a line from a log-file, but simply skips the line.
- . mistake (user)
- When a user does something wrong, but what is correctable by smart behavior of the program. For instance, in some configuration file, you can fill-in "yes" or "no", but the user wrote "yeah". The program interprets this as "yes", producing a mistake message as warning. It is much nicer to tell someone that he/she made a mistake, than to call that an error.
- . error (user)
- The user did something wrong, which is not automatically correctable or the program is not willing to correct it automatically for reasons of code quality. For instance, an unknown option flag is given on the command-line. These are configuration issues, and have no useful value in $!. The program will be stopped, usually before taken off.
- . fault (system)
- The program encountered a situation where it has no work-around. For instance, a file cannot be opened to be written. The cause of that problem can be some user error (i.e. wrong filename), or external (you accidentally removed a directory yesterday). In any case, the $! ($ERRNO) variable is set here.
- . alert (system)
- Some external cause disturbs the execution of the program, but the program stays alive and will try to continue operation. For instance, the connection to the database is lost. After a few attempts, the database can be reached and the program continues as if nothing happened. The cause is external, so $! is set. Usually, a system administrator needs to be informed about the problem.
- . failure (system)
- Some external cause makes it impossible for this program to continue. $! is set, and usually the system administrator wants to be informed. The program will die. The difference with "fault" is subtile and not always clear. A fault reports an error returned by an operating system call, where the failure would report an operational problem, like a failing mount.
- . panic (program)
- All above report classes are expected: some predictable situation is encountered, and therefore a message is produced. However, programs often do some internal checking. Of course, these conditions should never be triggered, but if they do... then we can only stop. For instance, in an OO perl module, the base class requires all sub-classes to implement a certain method. The base class will produce a stub method with triggers a panic when called. The non-dieing version of this test "assert".
Perl5 Log::Dispatch Syslog Log4Perl Log::Report print 0,debug debug debug trace print 0,debug debug debug assert print 1,info info info info warn\n 2,notice notice info notice warn 3,warning warn warn mistake carp 3,warning warn warn warning die\n 4,error err error error die 5,critical crit fatal fault croak 6,alert alert fatal alert croak 7,emergency emerg fatal failure confess 7,emergency emerg fatal panicRun modes The run-mode change which messages are passed to a dispatcher, but from a different angle than the dispatch filters; the mode changes behavioral aspects of the messages, which are described in detail in "Processing the message" in Log::Report::Dispatcher. However, it should behave as you expect: the DEBUG mode shows more than the VERBOSE mode, and both show more than the NORMAL mode. Exceptions The simple view on live says: you 're dead when you die. However, more complex situations try to revive the dead. Typically, the "die" is considered a terminating exception, but not terminating the whole program, but only some logical block. Of course, a wrapper round that block must decide what to do with these emerging problems. Java-like languages do not "die" but throw exceptions which contain the information about what went wrong. Perl modules like "Exception::Class" simulate this. It's a hassle to create exception class objects for each emerging problem, and the same amount of work to walk through all the options. Log::Report follows a simpler scheme. Fatal messages will "die", which is caught with "eval", just the Perl way (used invisible to you). However, the wrapper gets its hands on the message as the user has specified it: untranslated, with all unprocessed parameters still at hand.
try { fault __x "cannot open file {file}", file => $fn }; if($@) # is Log::Report::Dispatcher::Try { my $cause = $@->wasFatal; # is Log::Report::Exception $cause->throw if $cause->message->msgid =~ m/ open /; # all other problems ignored }See Log::Report::Dispatcher::Try and Log::Report::Exception.
Comparison¶
die/warn/Carp A typical perl5 program can look like this:my $dir = '/etc'; File::Spec->file_name is_absolute($dir) or die "ERROR: directory name must be absolute.\n"; -d $dir or die "ERROR: what platform are you on?"; until(opendir DIR, $dir) { warn "ERROR: cannot read system directory $dir: $!"; sleep 60; } print "Processing directory $dir\n" if $verbose; while(defined(my $file = readdir DIR)) { if($file =~ m/\.bak$/) { warn "WARNING: found backup file $dir/$f\n"; next; } die "ERROR: file $dir/$file is binary" if $debug && -B "$dir/$file"; print "DEBUG: processing file $dir/$file\n" if $debug; open FILE, "<", "$dir/$file" or die "ERROR: cannot read from $dir/$f: $!"; close FILE or croak "ERROR: read errors in $dir/$file: $!"; }Where "die", "warn", and "print" are used for various tasks. With "Log::Report", you would write
use Log::Report; # can be left-out when there is no debug/verbose dispatcher PERL => 'default', mode => 'DEBUG'; my $dir = '/etc'; File::Spec->file_name is_absolute($dir) or mistake "directory name must be absolute"; -d $dir or panic "what platform are you on?"; until(opendir DIR, $dir) { alert "cannot read system directory $dir"; sleep 60; } info "Processing directory $dir"; while(defined(my $file = readdir DIR)) { if($file =~ m/\.bak$/) { notice "found backup file $dir/$f"; next; } assert "file $dir/$file is binary" if -B "$dir/$file"; trace "processing file $dir/$file"; unless(open FILE, "<", "$dir/$file") { error "no permission to read from $dir/$f" if $!==ENOPERM; fault "unable to read from $dir/$f"; } close FILE or failure "read errors in $dir/$file"; }A lot of things are quite visibly different, and there are a few smaller changes. There is no need for a new-line after the text of the message. When applicable (error about system problem), then the $! is added automatically. Log::Dispatch and Log::Log4perl The two major logging frameworks for Perl are Log::Dispatch and Log::Log4perl; both provide a pluggable logging interface. Both frameworks do not have (gettext or maketext) language translation support, which has various consequences. When you wish for to report in some other language, it must be translated before the logging function is called. This may mean that an error message is produced in Chinese, and therefore also ends-up in the syslog file in Chinese. When this is not your language, you have a problem. Log::Report translates only in the back-end, which means that the user may get the message in Chinese, but you get your report in your beloved Dutch. When no dispatcher needs to report the message, then no time is lost in translating. With both logging frameworks, you use terminology comparable to syslog: the module programmer determines the seriousness of the error message, not the application which integrates multiple modules. This is the way perl programs usually work, but often the cause for inconsequent user interaction. Locale::gettext and Locate::TextDomain Both on GNU gettext based implementations can be used as translation frameworks. Locale::TextDomain syntax is supported, with quite some extensions. Read the excellent documentation of Locale::Textdomain. Only the tried access via "$__" and "%__" are not supported. The main difference with these modules is the moment when the translation takes place. In Locale::TextDomain, an "__x()" will result in an immediate translation request via "gettext()". "Log::Report"'s version of "__x()" will only capture what needs to be translated in an object. When the object is used in a print statement, only then the translation will take place. This is needed to offer ways to send different translations of the message to different destinations. To be able to postpone translation, objects are returned which stringify into the translated text.
DIAGNOSTICS¶
- Error: in SCALAR context, only one dispatcher name accepted
- The dispatcher() method returns the Log::Report::Dispatcher objects which it has accessed. When multiple names where given, it wishes to return a LIST of objects, not the count of them.
SEE ALSO¶
This module is part of Log-Report distribution version 1.05, built on June 24, 2014. Website: http://perl.overmeer.net/log-report/LICENSE¶
Copyrights 2007-2014 by [Mark Overmeer]. For other contributors see ChangeLog. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See http://www.perl.com/perl/misc/Artistic.html2014-06-24 | perl v5.18.2 |