perllocale.1

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

.Sp
Subpatterns, either delivered as a list-context result or as \f(CW$1\fR etc.
are tainted if \f(CW\*(C`use locale\*(C'\fR is in effect, and the subpattern regular
expression contains \f(CW\*(C`\ew\*(C'\fR (to match an alphanumeric character), \f(CW\*(C`\eW\*(C'\fR
(non-alphanumeric character), \f(CW\*(C`\es\*(C'\fR (whitespace character), or \f(CW\*(C`\eS\*(C'\fR
(non whitespace character).  The matched-pattern variable, $&, $`
(pre-match), $' (post-match), and $+ (last match) are also tainted if
\&\f(CW\*(C`use locale\*(C'\fR is in effect and the regular expression contains \f(CW\*(C`\ew\*(C'\fR,
\&\f(CW\*(C`\eW\*(C'\fR, \f(CW\*(C`\es\*(C'\fR, or \f(CW\*(C`\eS\*(C'\fR.
.IP "\(bu" 4
\&\fBSubstitution operator\fR (\f(CW\*(C`s///\*(C'\fR):
.Sp
Has the same behavior as the match operator.  Also, the left
operand of \f(CW\*(C`=~\*(C'\fR becomes tainted when \f(CW\*(C`use locale\*(C'\fR in effect
if modified as a result of a substitution based on a regular
expression match involving \f(CW\*(C`\ew\*(C'\fR, \f(CW\*(C`\eW\*(C'\fR, \f(CW\*(C`\es\*(C'\fR, or \f(CW\*(C`\eS\*(C'\fR; or of
case-mapping with \f(CW\*(C`\el\*(C'\fR, \f(CW\*(C`\eL\*(C'\fR,\f(CW\*(C`\eu\*(C'\fR or \f(CW\*(C`\eU\*(C'\fR.
.IP "\(bu" 4
\&\fBOutput formatting functions\fR (\fIprintf()\fR and \fIwrite()\fR):
.Sp
Results are never tainted because otherwise even output from print,
for example \f(CW\*(C`print(1/7)\*(C'\fR, should be tainted if \f(CW\*(C`use locale\*(C'\fR is in
effect.
.IP "\(bu" 4
\&\fBCase-mapping functions\fR (\fIlc()\fR, \fIlcfirst()\fR, \fIuc()\fR, \fIucfirst()\fR):
.Sp
Results are tainted if \f(CW\*(C`use locale\*(C'\fR is in effect.
.IP "\(bu" 4
\&\fB\s-1POSIX\s0 locale-dependent functions\fR (\fIlocaleconv()\fR, \fIstrcoll()\fR,
\&\fIstrftime()\fR, \fIstrxfrm()\fR):
.Sp
Results are never tainted.
.IP "\(bu" 4
\&\fB\s-1POSIX\s0 character class tests\fR (\fIisalnum()\fR, \fIisalpha()\fR, \fIisdigit()\fR,
\&\fIisgraph()\fR, \fIislower()\fR, \fIisprint()\fR, \fIispunct()\fR, \fIisspace()\fR, \fIisupper()\fR,
\&\fIisxdigit()\fR):
.Sp
True/false results are never tainted.
.PP
Three examples illustrate locale-dependent tainting.
The first program, which ignores its locale, won't run: a value taken
directly from the command line may not be used to name an output file
when taint checks are enabled.
.PP
.Vb 2
\&        #/usr/local/bin/perl \-T
\&        # Run with taint checking
\&
\&        # Command line sanity check omitted...
\&        $tainted_output_file = shift;
\&
\&        open(F, ">$tainted_output_file")
\&            or warn "Open of $untainted_output_file failed: $!\en";
.Ve
.PP
The program can be made to run by \*(L"laundering\*(R" the tainted value through
a regular expression: the second example\*(--which still ignores locale
information\*(--runs, creating the file named on its command line
if it can.
.PP
.Vb 1
\&        #/usr/local/bin/perl \-T
\&
\&        $tainted_output_file = shift;
\&        $tainted_output_file =~ m%[\ew/]+%;
\&        $untainted_output_file = $&;
\&
\&        open(F, ">$untainted_output_file")
\&            or warn "Open of $untainted_output_file failed: $!\en";
.Ve
.PP
Compare this with a similar but locale-aware program:
.PP
.Vb 1
\&        #/usr/local/bin/perl \-T
\&
\&        $tainted_output_file = shift;
\&        use locale;
\&        $tainted_output_file =~ m%[\ew/]+%;
\&        $localized_output_file = $&;
\&
\&        open(F, ">$localized_output_file")
\&            or warn "Open of $localized_output_file failed: $!\en";
.Ve
.PP
This third program fails to run because $& is tainted: it is the result
of a match involving \f(CW\*(C`\ew\*(C'\fR while \f(CW\*(C`use locale\*(C'\fR is in effect.
.SH "ENVIRONMENT"
.IX Header "ENVIRONMENT"
.IP "\s-1PERL_BADLANG\s0" 12
.IX Item "PERL_BADLANG"
A string that can suppress Perl's warning about failed locale settings
at startup.  Failure can occur if the locale support in the operating
system is lacking (broken) in some way\*(--or if you mistyped the name of
a locale when you set up your environment.  If this environment
variable is absent, or has a value that does not evaluate to integer
zero\*(--that is, \*(L"0\*(R" or ""\-\- Perl will complain about locale setting
failures.
.Sp
\&\fB\s-1NOTE\s0\fR: \s-1PERL_BADLANG\s0 only gives you a way to hide the warning message.
The message tells about some problem in your system's locale support,
and you should investigate what the problem is.
.PP
The following environment variables are not specific to Perl: They are
part of the standardized (\s-1ISO\s0 C, \s-1XPG4\s0, \s-1POSIX\s0 1.c) \fIsetlocale()\fR method
for controlling an application's opinion on data.
.IP "\s-1LC_ALL\s0" 12
.IX Item "LC_ALL"
\&\f(CW\*(C`LC_ALL\*(C'\fR is the \*(L"override-all\*(R" locale environment variable. If
set, it overrides all the rest of the locale environment variables.
.IP "\s-1LANGUAGE\s0" 12
.IX Item "LANGUAGE"
\&\fB\s-1NOTE\s0\fR: \f(CW\*(C`LANGUAGE\*(C'\fR is a \s-1GNU\s0 extension, it affects you only if you
are using the \s-1GNU\s0 libc.  This is the case if you are using e.g. Linux.
If you are using \*(L"commercial\*(R" UNIXes you are most probably \fInot\fR
using \s-1GNU\s0 libc and you can ignore \f(CW\*(C`LANGUAGE\*(C'\fR.
.Sp
However, in the case you are using \f(CW\*(C`LANGUAGE\*(C'\fR: it affects the
language of informational, warning, and error messages output by
commands (in other words, it's like \f(CW\*(C`LC_MESSAGES\*(C'\fR) but it has higher
priority than \s-1LC_ALL\s0.  Moreover, it's not a single value but
instead a \*(L"path\*(R" (\*(L":\*(R"\-separated list) of \fIlanguages\fR (not locales).
See the \s-1GNU\s0 \f(CW\*(C`gettext\*(C'\fR library documentation for more information.
.IP "\s-1LC_CTYPE\s0" 12
.IX Item "LC_CTYPE"
In the absence of \f(CW\*(C`LC_ALL\*(C'\fR, \f(CW\*(C`LC_CTYPE\*(C'\fR chooses the character type
locale.  In the absence of both \f(CW\*(C`LC_ALL\*(C'\fR and \f(CW\*(C`LC_CTYPE\*(C'\fR, \f(CW\*(C`LANG\*(C'\fR
chooses the character type locale.
.IP "\s-1LC_COLLATE\s0" 12
.IX Item "LC_COLLATE"
In the absence of \f(CW\*(C`LC_ALL\*(C'\fR, \f(CW\*(C`LC_COLLATE\*(C'\fR chooses the collation
(sorting) locale.  In the absence of both \f(CW\*(C`LC_ALL\*(C'\fR and \f(CW\*(C`LC_COLLATE\*(C'\fR,
\&\f(CW\*(C`LANG\*(C'\fR chooses the collation locale.
.IP "\s-1LC_MONETARY\s0" 12
.IX Item "LC_MONETARY"
In the absence of \f(CW\*(C`LC_ALL\*(C'\fR, \f(CW\*(C`LC_MONETARY\*(C'\fR chooses the monetary
formatting locale.  In the absence of both \f(CW\*(C`LC_ALL\*(C'\fR and \f(CW\*(C`LC_MONETARY\*(C'\fR,
\&\f(CW\*(C`LANG\*(C'\fR chooses the monetary formatting locale.
.IP "\s-1LC_NUMERIC\s0" 12
.IX Item "LC_NUMERIC"
In the absence of \f(CW\*(C`LC_ALL\*(C'\fR, \f(CW\*(C`LC_NUMERIC\*(C'\fR chooses the numeric format
locale.  In the absence of both \f(CW\*(C`LC_ALL\*(C'\fR and \f(CW\*(C`LC_NUMERIC\*(C'\fR, \f(CW\*(C`LANG\*(C'\fR
chooses the numeric format.
.IP "\s-1LC_TIME\s0" 12
.IX Item "LC_TIME"
In the absence of \f(CW\*(C`LC_ALL\*(C'\fR, \f(CW\*(C`LC_TIME\*(C'\fR chooses the date and time
formatting locale.  In the absence of both \f(CW\*(C`LC_ALL\*(C'\fR and \f(CW\*(C`LC_TIME\*(C'\fR,
\&\f(CW\*(C`LANG\*(C'\fR chooses the date and time formatting locale.
.IP "\s-1LANG\s0" 12
.IX Item "LANG"
\&\f(CW\*(C`LANG\*(C'\fR is the \*(L"catch-all\*(R" locale environment variable. If it is set, it
is used as the last resort after the overall \f(CW\*(C`LC_ALL\*(C'\fR and the
category-specific \f(CW\*(C`LC_...\*(C'\fR.
.Sh "Examples"
.IX Subsection "Examples"
The \s-1LC_NUMERIC\s0 controls the numeric output:
.PP
.Vb 4
\&        use locale;
\&        use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
\&        setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
\&        printf "%g\en", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
.Ve
.PP
and also how strings are parsed by \fIPOSIX::strtod()\fR as numbers:
.PP
.Vb 5
\&        use locale;
\&        use POSIX qw(locale_h strtod);
\&        setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
\&        my $x = strtod("2,34") + 5;
\&        print $x, "\en"; # Probably shows 7,34.
.Ve
.SH "NOTES"
.IX Header "NOTES"
.Sh "Backward compatibility"
.IX Subsection "Backward compatibility"
Versions of Perl prior to 5.004 \fBmostly\fR ignored locale information,
generally behaving as if something similar to the \f(CW"C"\fR locale were
always in force, even if the program environment suggested otherwise
(see \*(L"The setlocale function\*(R").  By default, Perl still behaves this
way for backward compatibility.  If you want a Perl application to pay
attention to locale information, you \fBmust\fR use the \f(CW\*(C`use\ locale\*(C'\fR
pragma (see \*(L"The use locale pragma\*(R") to instruct it to do so.
.PP
Versions of Perl from 5.002 to 5.003 did use the \f(CW\*(C`LC_CTYPE\*(C'\fR
information if available; that is, \f(CW\*(C`\ew\*(C'\fR did understand what
were the letters according to the locale environment variables.
The problem was that the user had no control over the feature:
if the C library supported locales, Perl used them.
.Sh "I18N:Collate obsolete"
.IX Subsection "I18N:Collate obsolete"
In versions of Perl prior to 5.004, per-locale collation was possible
using the \f(CW\*(C`I18N::Collate\*(C'\fR library module.  This module is now mildly
obsolete and should be avoided in new applications.  The \f(CW\*(C`LC_COLLATE\*(C'\fR
functionality is now integrated into the Perl core language: One can
use locale-specific scalar data completely normally with \f(CW\*(C`use locale\*(C'\fR,
so there is no longer any need to juggle with the scalar references of
\&\f(CW\*(C`I18N::Collate\*(C'\fR.
.Sh "Sort speed and memory use impacts"
.IX Subsection "Sort speed and memory use impacts"
Comparing and sorting by locale is usually slower than the default
sorting; slow-downs of two to four times have been observed.  It will
also consume more memory: once a Perl scalar variable has participated
in any string comparison or sorting operation obeying the locale
collation rules, it will take 3\-15 times more memory than before.  (The
exact multiplier depends on the string's contents, the operating system
and the locale.) These downsides are dictated more by the operating
system's implementation of the locale system than by Perl.
.Sh "\fIwrite()\fP and \s-1LC_NUMERIC\s0"
.IX Subsection "write() and LC_NUMERIC"
Formats are the only part of Perl that unconditionally use information
from a program's locale; if a program's environment specifies an
\&\s-1LC_NUMERIC\s0 locale, it is always used to specify the decimal point
character in formatted output.  Formatted output cannot be controlled by
\&\f(CW\*(C`use locale\*(C'\fR because the pragma is tied to the block structure of the
program, and, for historical reasons, formats exist outside that block
structure.
.Sh "Freely available locale definitions"
.IX Subsection "Freely available locale definitions"
There is a large collection of locale definitions at
ftp://dkuug.dk/i18n/WG15\-collection .  You should be aware that it is
unsupported, and is not claimed to be fit for any purpose.  If your
system allows installation of arbitrary locales, you may find the
definitions useful as they are, or as a basis for the development of
your own locales.
.Sh "I18n and l10n"
.IX Subsection "I18n and l10n"
\&\*(L"Internationalization\*(R" is often abbreviated as \fBi18n\fR because its first
and last letters are separated by eighteen others.  (You may guess why
the internalin ... internaliti ... i18n tends to get abbreviated.)  In
the same way, \*(L"localization\*(R" is often abbreviated to \fBl10n\fR.
.Sh "An imperfect standard"
.IX Subsection "An imperfect standard"
Internationalization, as defined in the C and \s-1POSIX\s0 standards, can be
criticized as incomplete, ungainly, and having too large a granularity.
(Locales apply to a whole process, when it would arguably be more useful
to have them apply to a single thread, window group, or whatever.)  They
also have a tendency, like standards groups, to divide the world into
nations, when we all know that the world can equally well be divided
into bankers, bikers, gamers, and so on.  But, for now, it's the only
standard we've got.  This may be construed as a bug.
.SH "Unicode and UTF\-8"
.IX Header "Unicode and UTF-8"
The support of Unicode is new starting from Perl version 5.6, and
more fully implemented in the version 5.8.  See perluniintro and
perlunicode for more details.
.PP
Usually locale settings and Unicode do not affect each other, but
there are exceptions, see \*(L"Locales\*(R" in perlunicode for examples.
.SH "BUGS"
.IX Header "BUGS"
.Sh "Broken systems"
.IX Subsection "Broken systems"
In certain systems, the operating system's locale support
is broken and cannot be fixed or used by Perl.  Such deficiencies can
and will result in mysterious hangs and/or Perl core dumps when the
\&\f(CW\*(C`use locale\*(C'\fR is in effect.  When confronted with such a system,
please report in excruciating detail to <\[e-mail]\fR>, and
complain to your vendor: bug fixes may exist for these problems
in your operating system.  Sometimes such bug fixes are called an
operating system upgrade.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
I18N::Langinfo, perluniintro, perlunicode, open,
\&\*(L"isalnum\*(R" in \s-1POSIX\s0, \*(L"isalpha\*(R" in \s-1POSIX\s0,
\&\*(L"isdigit\*(R" in \s-1POSIX\s0, \*(L"isgraph\*(R" in \s-1POSIX\s0, \*(L"islower\*(R" in \s-1POSIX\s0,
\&\*(L"isprint\*(R" in \s-1POSIX\s0, \*(L"ispunct\*(R" in \s-1POSIX\s0, \*(L"isspace\*(R" in \s-1POSIX\s0,
\&\*(L"isupper\*(R" in \s-1POSIX\s0, \*(L"isxdigit\*(R" in \s-1POSIX\s0, \*(L"localeconv\*(R" in \s-1POSIX\s0,
\&\*(L"setlocale\*(R" in \s-1POSIX\s0, \*(L"strcoll\*(R" in \s-1POSIX\s0, \*(L"strftime\*(R" in \s-1POSIX\s0,
\&\*(L"strtod\*(R" in \s-1POSIX\s0, \*(L"strxfrm\*(R" in \s-1POSIX\s0.
.SH "HISTORY"
.IX Header "HISTORY"
Jarkko Hietaniemi's original \fIperli18n.pod\fR heavily hacked by Dominic
Dunlop, assisted by the perl5\-porters.  Prose worked over a bit by
Tom Christiansen.
.PP
Last update: Thu Jun 11 08:44:13 \s-1MDT\s0 1998