POSIX::asctime pod: Note it always returns English

[perl5.git] / ext / POSIX / lib / POSIX.pod

diff --git a/ext/POSIX/lib/POSIX.pod b/ext/POSIX/lib/POSIX.pod
index 4393702..a92a20c 100644 (file)
--- a/ext/POSIX/lib/POSIX.pod
+++ b/ext/POSIX/lib/POSIX.pod
@@ -24,7 +24,7 @@ interfaces.
 This document gives a condensed list of the features available in the POSIX
 module.  Consult your operating system's manpages for general information on
 most features.  Consult L<perlfunc> for functions which are noted as being
 This document gives a condensed list of the features available in the POSIX
 module.  Consult your operating system's manpages for general information on
 most features.  Consult L<perlfunc> for functions which are noted as being

-identical to Perl's builtin functions.
+identical or almost identical to Perl's builtin functions.

 
 The first section describes POSIX functions from the 1003.1 specification.
 The second section describes some classes for signal objects, TTY objects,
 
 The first section describes POSIX functions from the 1003.1 specification.
 The second section describes some classes for signal objects, TTY objects,


@@ -81,8 +81,13 @@ if the handler does not return normally (it e.g.  does a C<longjmp>).
 
 =item C<abs>
 
 
 =item C<abs>
 

-This is identical to Perl's builtin C<abs()> function, returning
-the absolute value of its numerical argument.
+This is identical to Perl's builtin C<abs()> function, returning the absolute
+value of its numerical argument (except that C<POSIX::abs()> must be provided
+an explicit value (rather than relying on an implicit C<$_>):
+
+    $absolute_value = POSIX::abs(42);   # good
+
+    $absolute_value = POSIX::abs();     # throws exception

 
 =item C<access>
 
 
 =item C<access>
 


@@ -106,12 +111,17 @@ the arcus cosine of its numerical argument.  See also L<Math::Trig>.
 
 This is identical to the C function C<acosh()>, returning the
 hyperbolic arcus cosine of its numerical argument [C99].  See also
 
 This is identical to the C function C<acosh()>, returning the
 hyperbolic arcus cosine of its numerical argument [C99].  See also

-L<Math::Trig>.
+L<Math::Trig>.  Added in Perl v5.22.

 
 =item C<alarm>
 
 
 =item C<alarm>
 

-This is identical to Perl's builtin C<alarm()> function,
-either for arming or disarming the C<SIGARLM> timer.
+This is identical to Perl's builtin C<alarm()> function, either for arming or
+disarming the C<SIGARLM> timer, except that C<POSIX::alarm()> must be provided
+an explicit value (rather than relying on an implicit C<$_>):
+
+    POSIX::alarm(3)     # good
+
+    POSIX::alarm()      # throws exception

 
 =item C<asctime>
 
 
 =item C<asctime>
 


@@ -129,6 +139,10 @@ The C<$mon> is zero-based: January equals C<0>.  The C<$year> is
 1900-based: 2001 equals C<101>.  C<$wday> and C<$yday> default to zero
 (and are usually ignored anyway), and C<$isdst> defaults to -1.
 
 1900-based: 2001 equals C<101>.  C<$wday> and C<$yday> default to zero
 (and are usually ignored anyway), and C<$isdst> defaults to -1.
 

+Note the result is always in English.  Use C<L</strftime>> instead to
+get a result suitable for the current locale.  That function's C<%c>
+format yields the locale's preferred representation.
+

 =item C<asin>
 
 This is identical to the C function C<asin()>, returning
 =item C<asin>
 
 This is identical to the C function C<asin()>, returning


@@ -138,7 +152,7 @@ the arcus sine of its numerical argument.  See also L<Math::Trig>.
 
 This is identical to the C function C<asinh()>, returning the
 hyperbolic arcus sine of its numerical argument [C99].  See also
 
 This is identical to the C function C<asinh()>, returning the
 hyperbolic arcus sine of its numerical argument [C99].  See also

-L<Math::Trig>.
+L<Math::Trig>.  Added in Perl v5.22.

 
 =item C<assert>
 
 
 =item C<assert>
 


@@ -154,7 +168,7 @@ arcus tangent of its numerical argument.  See also L<Math::Trig>.
 
 This is identical to the C function C<atanh()>, returning the
 hyperbolic arcus tangent of its numerical argument [C99].  See also
 
 This is identical to the C function C<atanh()>, returning the
 hyperbolic arcus tangent of its numerical argument [C99].  See also

-L<Math::Trig>.
+L<Math::Trig>.  Added in Perl v5.22.

 
 =item C<atan2>
 
 
 =item C<atan2>
 


@@ -194,7 +208,7 @@ Not implemented.  C<calloc()> is C-specific.  Perl does memory management transp
 
 =item C<cbrt>
 
 
 =item C<cbrt>
 

-The cube root [C99].
+The cube root [C99].  Added in Perl v5.22.

 
 =item C<ceil>
 
 
 =item C<ceil>
 


@@ -203,13 +217,30 @@ integer value greater than or equal to the given numerical argument.
 
 =item C<chdir>
 
 
 =item C<chdir>
 

-This is identical to Perl's builtin C<chdir()> function, allowing
-one to change the working (default) directory, see L<perlfunc/chdir>.
+This is identical to Perl's builtin C<chdir()> function, allowing one to
+change the working (default) directory -- see L<perlfunc/chdir> -- with the
+exception that C<POSIX::chdir()> must be provided an explicit value (rather
+than relying on an implicit C<$_>):
+
+    $rv = POSIX::chdir('path/to/dir');      # good
+
+    $rv = POSIX::chdir();                   # throws exception

 
 =item C<chmod>
 
 This is identical to Perl's builtin C<chmod()> function, allowing
 
 =item C<chmod>
 
 This is identical to Perl's builtin C<chmod()> function, allowing

-one to change file and directory permissions, see L<perlfunc/chmod>.
+one to change file and directory permissions -- see L<perlfunc/chmod> -- with
+the exception that C<POSIX::chmod()> can only change one file at a time
+(rather than a list of files):
+
+    $c = chmod 0664, $file1, $file2;          # good
+
+    $c = POSIX::chmod 0664, $file1;           # throws exception
+
+    $c = POSIX::chmod 0664, $file1, $file2;   # throws exception
+
+As with the built-in C<chmod()>, C<$file> may be a filename or a file
+handle.

 
 =item C<chown>
 
 
 =item C<chown>
 


@@ -256,7 +287,7 @@ the hyperbolic cosine of its numeric argument.  See also L<Math::Trig>.
 
 =item C<copysign>
 
 
 =item C<copysign>
 

-Returns C<x> but with the sign of C<y> [C99].
+Returns C<x> but with the sign of C<y> [C99].  Added in Perl v5.22.

 
  $x_with_sign_of_y = POSIX::copysign($x, $y);
 
 
  $x_with_sign_of_y = POSIX::copysign($x, $y);
 


@@ -283,12 +314,15 @@ Generates the path name for the controlling terminal.
 This is identical to the C function C<ctime()> and equivalent
 to C<asctime(localtime(...))>, see L</asctime> and L</localtime>.
 
 This is identical to the C function C<ctime()> and equivalent
 to C<asctime(localtime(...))>, see L</asctime> and L</localtime>.
 

-=item C<cuserid>
+=item C<cuserid> [POSIX.1-1988]

 
 Get the login name of the owner of the current process.
 
        $name = POSIX::cuserid();
 
 
 Get the login name of the owner of the current process.
 
        $name = POSIX::cuserid();
 

+Note: this function has not been specified by POSIX since 1990 and is included
+only for backwards compatibility. New code should use L<C<getlogin()>|perlfunc/getlogin> instead.
+

 =item C<difftime>
 
 This is identical to the C function C<difftime()>, for returning
 =item C<difftime>
 
 This is identical to the C function C<difftime()>, for returning


@@ -322,11 +356,11 @@ Returns C<undef> on failure.
 
 =item C<erf>
 
 
 =item C<erf>
 

-The error function [C99].
+The error function [C99].  Added in Perl v5.22.

 
 =item C<erfc>
 
 
 =item C<erfc>
 

-The complementary error function [C99].
+The complementary error function [C99].  Added in Perl v5.22.

 
 =item C<errno>
 
 
 =item C<errno>
 


@@ -374,6 +408,7 @@ see L<perlfunc/exp>.
 =item C<expm1>
 
 Equivalent to C<exp(x) - 1>, but more precise for small argument values [C99].
 =item C<expm1>
 
 Equivalent to C<exp(x) - 1>, but more precise for small argument values [C99].

+Added in Perl v5.22.

 
 See also L</log1p>.
 
 
 See also L</log1p>.
 


@@ -433,35 +468,40 @@ integer value less than or equal to the numerical argument.
 =item C<fdim>
 
 "Positive difference", S<C<x - y>> if S<C<x E<gt> y>>, zero otherwise [C99].
 =item C<fdim>
 
 "Positive difference", S<C<x - y>> if S<C<x E<gt> y>>, zero otherwise [C99].

+Added in Perl v5.22.

 
 =item C<fegetround>
 
 Returns the current floating point rounding mode, one of
 
 
 =item C<fegetround>
 
 Returns the current floating point rounding mode, one of
 

-  FE_TONEAREST FE_TOWARDZERO FE_UPWARD FE_UPWARD
+  FE_TONEAREST FE_TOWARDZERO FE_UPWARD FE_DOWNWARD

 
 C<FE_TONEAREST> is like L</round>, C<FE_TOWARDZERO> is like L</trunc> [C99].
 
 C<FE_TONEAREST> is like L</round>, C<FE_TOWARDZERO> is like L</trunc> [C99].

+Added in Perl v5.22.

 
 =item C<fesetround>
 
 
 =item C<fesetround>
 

-Sets the floating point rounding mode, see L</fegetround> [C99].
+Sets the floating point rounding mode, see L</fegetround> [C99].  Added in
+Perl v5.22.

 
 =item C<fma>
 
 "Fused multiply-add", S<C<x * y + z>>, possibly faster (and less lossy)
 
 =item C<fma>
 
 "Fused multiply-add", S<C<x * y + z>>, possibly faster (and less lossy)

-than the explicit two operations [C99].
+than the explicit two operations [C99].  Added in Perl v5.22.

 
  my $fused = POSIX::fma($x, $y, $z);
 
 =item C<fmax>
 
 Maximum of C<x> and C<y>, except when either is C<NaN>, returns the other [C99].
 
  my $fused = POSIX::fma($x, $y, $z);
 
 =item C<fmax>
 
 Maximum of C<x> and C<y>, except when either is C<NaN>, returns the other [C99].

+Added in Perl v5.22.

 
  my $min = POSIX::fmax($x, $y);
 
 =item C<fmin>
 
 Minimum of C<x> and C<y>, except when either is C<NaN>, returns the other [C99].
 
  my $min = POSIX::fmax($x, $y);
 
 =item C<fmin>
 
 Minimum of C<x> and C<y>, except when either is C<NaN>, returns the other [C99].

+Added in Perl v5.22.

 
  my $min = POSIX::fmin($x, $y);
 
 
  my $min = POSIX::fmin($x, $y);
 


@@ -508,6 +548,7 @@ telling the class of the argument [C99].  C<FP_INFINITE> is positive
 or negative infinity, C<FP_NAN> is not-a-number.  C<FP_SUBNORMAL>
 means subnormal numbers (also known as denormals), very small numbers
 with low precision. C<FP_ZERO> is zero.  C<FP_NORMAL> is all the rest.
 or negative infinity, C<FP_NAN> is not-a-number.  C<FP_SUBNORMAL>
 means subnormal numbers (also known as denormals), very small numbers
 with low precision. C<FP_ZERO> is zero.  C<FP_NORMAL> is all the rest.

+Added in Perl v5.22.

 
 =item C<fprintf>
 
 
 =item C<fprintf>
 


@@ -634,7 +675,7 @@ L<perlfunc/getlogin>.
        use POSIX ':nan_payload';
        getpayload($var)
 
        use POSIX ':nan_payload';
        getpayload($var)
 

-Returns the C<NaN> payload.
+Returns the C<NaN> payload.  Added in Perl v5.24.

 
 Note the API instability warning in L</setpayload>.
 
 
 Note the API instability warning in L</setpayload>.
 


@@ -691,11 +732,11 @@ see L<perlfunc/gmtime>.
 =item C<hypot>
 
 Equivalent to C<S<sqrt(x * x + y * y)>> except more stable on very large
 =item C<hypot>
 
 Equivalent to C<S<sqrt(x * x + y * y)>> except more stable on very large

-or very small arguments [C99].
+or very small arguments [C99].  Added in Perl v5.22.

 
 =item C<ilogb>
 
 
 =item C<ilogb>
 

-Integer binary logarithm [C99]
+Integer binary logarithm [C99].  Added in Perl v5.22.

 
 For example C<ilogb(20)> is 4, as an integer.
 
 
 For example C<ilogb(20)> is 4, as an integer.
 


@@ -713,13 +754,13 @@ See also L</isinf>, and L</fpclassify>.
 
 =item C<isalnum>
 
 
 =item C<isalnum>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:alnum:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isalpha>
 
 matching against S<C<qr/ ^ [[:alnum:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isalpha>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:alpha:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 matching against S<C<qr/ ^ [[:alpha:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 


@@ -730,26 +771,26 @@ to a tty.  Similar to the C<-t> operator, see L<perlfunc/-X>.
 
 =item C<iscntrl>
 
 
 =item C<iscntrl>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:cntrl:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isdigit>
 
 matching against S<C<qr/ ^ [[:cntrl:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isdigit>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:digit:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isfinite>
 
 Returns true if the argument is a finite number (that is, not an
 matching against S<C<qr/ ^ [[:digit:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isfinite>
 
 Returns true if the argument is a finite number (that is, not an

-infinity, or the not-a-number) [C99].
+infinity, or the not-a-number) [C99].  Added in Perl v5.22.

 
 See also L</isinf>, L</isnan>, and L</fpclassify>.
 
 =item C<isgraph>
 
 
 See also L</isinf>, L</isnan>, and L</fpclassify>.
 
 =item C<isgraph>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:graph:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 matching against S<C<qr/ ^ [[:graph:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 


@@ -758,23 +799,26 @@ to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 (Also C<isgreaterequal>, C<isless>, C<islessequal>, C<islessgreater>,
 C<isunordered>)
 
 (Also C<isgreaterequal>, C<isless>, C<islessequal>, C<islessgreater>,
 C<isunordered>)
 

-Floating point comparisons which handle the C<NaN> [C99].
+Floating point comparisons which handle the C<NaN> [C99].  Added in Perl
+v5.22.

 
 =item C<isinf>
 
 Returns true if the argument is an infinity (positive or negative) [C99].
 
 =item C<isinf>
 
 Returns true if the argument is an infinity (positive or negative) [C99].

+Added in Perl v5.22.

 
 See also L</Inf>, L</isnan>, L</isfinite>, and L</fpclassify>.
 
 =item C<islower>
 
 
 See also L</Inf>, L</isnan>, L</isfinite>, and L</fpclassify>.
 
 =item C<islower>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:lower:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isnan>
 
 matching against S<C<qr/ ^ [[:lower:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isnan>
 

-Returns true if the argument is C<NaN> (not-a-number) [C99].
+Returns true if the argument is C<NaN> (not-a-number) [C99].  Added in
+Perl v5.22.

 
 Note that you cannot test for "C<NaN>-ness" with
 
 
 Note that you cannot test for "C<NaN>-ness" with
 


@@ -787,19 +831,19 @@ See also L</nan>, L</NaN>, L</isinf>, and L</fpclassify>.
 =item C<isnormal>
 
 Returns true if the argument is normal (that is, not a subnormal/denormal,
 =item C<isnormal>
 
 Returns true if the argument is normal (that is, not a subnormal/denormal,

-and not an infinity, or a not-a-number) [C99].
+and not an infinity, or a not-a-number) [C99].  Added in Perl v5.22.

 
 See also L</isfinite>, and L</fpclassify>.
 
 =item C<isprint>
 
 
 See also L</isfinite>, and L</fpclassify>.
 
 =item C<isprint>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:print:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<ispunct>
 
 matching against S<C<qr/ ^ [[:print:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<ispunct>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:punct:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 matching against S<C<qr/ ^ [[:punct:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 


@@ -808,7 +852,7 @@ to use instead.  See L<perlrecharclass/POSIX Character Classes>.
        use POSIX ':nan_payload';
        issignaling($var, $payload)
 
        use POSIX ':nan_payload';
        issignaling($var, $payload)
 

-Return true if the argument is a I<signaling> NaN.
+Return true if the argument is a I<signaling> NaN.  Added in Perl v5.24.

 
 Note the API instability warning in L</setpayload>.
 
 
 Note the API instability warning in L</setpayload>.
 


@@ -816,19 +860,19 @@ See L</nan> for more discussion about C<NaN>.
 
 =item C<isspace>
 
 
 =item C<isspace>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:space:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isupper>
 
 matching against S<C<qr/ ^ [[:space:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isupper>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:upper:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isxdigit>
 
 matching against S<C<qr/ ^ [[:upper:]]+ $ /x>>, which you should convert
 to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 =item C<isxdigit>
 

-This function has been removed as of v5.24.  It was very similar to
+This function has been removed as of Perl v5.24.  It was very similar to

 matching against S<C<qr/ ^ [[:xdigit:]]+ $ /x>>, which you should
 convert to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 
 matching against S<C<qr/ ^ [[:xdigit:]]+ $ /x>>, which you should
 convert to use instead.  See L<perlrecharclass/POSIX Character Classes>.
 


@@ -880,24 +924,24 @@ C<ldiv()> is C-specific, use C</> and C<int()> instead.
 
 =item C<lgamma>
 
 
 =item C<lgamma>
 

-The logarithm of the Gamma function [C99].
+The logarithm of the Gamma function [C99].  Added in Perl v5.22.

 
 See also L</tgamma>.
 
 =item C<log1p>
 
 Equivalent to S<C<log(1 + x)>>, but more stable results for small argument
 
 See also L</tgamma>.
 
 =item C<log1p>
 
 Equivalent to S<C<log(1 + x)>>, but more stable results for small argument

-values [C99].
+values [C99].  Added in Perl v5.22.

 
 =item C<log2>
 
 
 =item C<log2>
 

-Logarithm base two [C99].
+Logarithm base two [C99].  Added in Perl v5.22.

 
 See also L</expm1>.
 
 =item C<logb>
 
 
 See also L</expm1>.
 
 =item C<logb>
 

-Integer binary logarithm [C99].
+Integer binary logarithm [C99].  Added in Perl v5.22.

 
 For example C<logb(20)> is 4, as a floating point number.
 
 
 For example C<logb(20)> is 4, as a floating point number.
 


@@ -911,10 +955,20 @@ for creating hard links into files, see L<perlfunc/link>.
 =item C<localeconv>
 
 Get numeric formatting information.  Returns a reference to a hash
 =item C<localeconv>
 
 Get numeric formatting information.  Returns a reference to a hash

-containing the current underlying locale's formatting values.  Users of this function
-should also read L<perllocale>, which provides a comprehensive
-discussion of Perl locale handling, including
+containing the formatting values of the locale that currently underlies
+the program, regardless of whether or not it is called from within the
+scope of a S<C<use locale>>.  Users of this function should also read
+L<perllocale>, which provides a comprehensive discussion of Perl locale
+handling, including

 L<a section devoted to this function|perllocale/The localeconv function>.
 L<a section devoted to this function|perllocale/The localeconv function>.

+Prior to Perl 5.28, or when operating in a non thread-safe environment,
+it should not be used in a threaded application unless it's certain that
+the underlying locale is C or POSIX.  This is because it otherwise
+changes the locale, which globally affects all threads simultaneously.
+Windows platforms starting with Visual Studio 2005 are mostly
+thread-safe, but use of this function in those prior to Visual Studio
+2015 can interfere with a thread that has called
+L<perlapi/switch_to_global_locale>.

 
 Here is how to query the database for the B<de> (Deutsch or German) locale.
 
 
 Here is how to query the database for the B<de> (Deutsch or German) locale.
 


@@ -958,7 +1012,15 @@ POSIX.1-2008 and are only available on systems that support them.
 =item C<localtime>
 
 This is identical to Perl's builtin C<localtime()> function for
 =item C<localtime>
 
 This is identical to Perl's builtin C<localtime()> function for

-converting seconds since the epoch to a date see L<perlfunc/localtime>.
+converting seconds since the epoch to a date see L<perlfunc/localtime> except
+that C<POSIX::localtime()> must be provided an explicit value (rather than
+relying on an implicit C<$_>):
+
+    @localtime = POSIX::localtime(time);    # good
+
+    @localtime = localtime();               # good
+
+    @localtime = POSIX::localtime();        # throws exception

 
 =item C<log>
 
 
 =item C<log>
 


@@ -1001,19 +1063,20 @@ Returns C<undef> on failure.
 Depending on the current floating point rounding mode, rounds the
 argument either toward nearest (like L</round>), toward zero (like
 L</trunc>), downward (toward negative infinity), or upward (toward
 Depending on the current floating point rounding mode, rounds the
 argument either toward nearest (like L</round>), toward zero (like
 L</trunc>), downward (toward negative infinity), or upward (toward

-positive infinity) [C99].
+positive infinity) [C99].  Added in Perl v5.22.

 
 For the rounding mode, see L</fegetround>.
 
 =item C<lround>
 
 
 For the rounding mode, see L</fegetround>.
 
 =item C<lround>
 

-Like L</round>, but as integer, as opposed to floating point [C99].
+Like L</round>, but as integer, as opposed to floating point [C99].  Added
+in Perl v5.22.

 
 See also L</ceil>, L</floor>, L</trunc>.
 
 Owing to an oversight, this is not currently exported by default, or as part of
 the C<:math_h_c99> export tag; importing it must therefore be done by explicit
 
 See also L</ceil>, L</floor>, L</trunc>.
 
 Owing to an oversight, this is not currently exported by default, or as part of
 the C<:math_h_c99> export tag; importing it must therefore be done by explicit

-name. This will be changed in Perl 5.26.
+name.

 
 =item C<malloc>
 
 
 =item C<malloc>
 


@@ -1021,25 +1084,64 @@ Not implemented.  C<malloc()> is C-specific.  Perl does memory management transp
 
 =item C<mblen>
 
 
 =item C<mblen>
 

-This is identical to the C function C<mblen()>.
-
-Core Perl does not have any support for the wide and multibyte
-characters of the C standards, except under UTF-8 locales, so this might
-be a rather useless function.
-
-However, Perl supports Unicode, see L<perluniintro>.
-
-=item C<mbstowcs>
-
-This is identical to the C function C<mbstowcs()>.
-
-See L</mblen>.
+This is the same as the C function C<mblen()> on unthreaded perls.  On
+threaded perls, it transparently (almost) substitutes the more
+thread-safe L<C<mbrlen>(3)>, if available, instead of C<mblen>.
+
+Core Perl does not have any support for wide and multibyte locales,
+except Unicode UTF-8 locales.  This function, in conjunction with
+L</mbtowc> and L</wctomb> may be used to roll your own decoding/encoding
+of other types of multi-byte locales.
+
+Use C<undef> as the first parameter to this function to get the effect
+of passing NULL as the first parameter to C<mblen>.  This resets any
+shift state to its initial value.  The return value is undefined if
+C<mbrlen> was substituted, so you should never rely on it.
+
+When the first parameter is a scalar containing a value that either is a
+PV string or can be forced into one, the return value is the number of
+bytes occupied by the first character of that string; or 0 if that first
+character is the wide NUL character; or negative if there is an error.
+This is based on the locale that currently underlies the program,
+regardless of whether or not the function is called from Perl code that
+is within the scope of S<C<use locale>>.  Perl makes no attempt at
+hiding from your code any differences in the C<errno> setting between
+C<mblen> and C<mbrlen>.  It does set C<errno> to 0 before calling them.
+
+The optional second parameter is ignored if it is larger than the
+actual length of the first parameter string.

 
 =item C<mbtowc>
 
 
 =item C<mbtowc>
 

-This is identical to the C function C<mbtowc()>.
-
-See L</mblen>.
+This is the same as the C function C<mbtowc()> on unthreaded perls.  On
+threaded perls, it transparently (almost) substitutes the more
+thread-safe L<C<mbrtowc>(3)>, if available, instead of C<mbtowc>.
+
+Core Perl does not have any support for wide and multibyte locales,
+except Unicode UTF-8 locales.  This function, in conjunction with
+L</mblen> and L</wctomb> may be used to roll your own decoding/encoding
+of other types of multi-byte locales.
+
+The first parameter is a scalar into which, upon success, the wide
+character represented by the multi-byte string contained in the second
+parameter is stored.  The optional third parameter is ignored if it is
+larger than the actual length of the second parameter string.
+
+Use C<undef> as the second parameter to this function to get the effect
+of passing NULL as the second parameter to C<mbtowc>.  This resets any
+shift state to its initial value.  The return value is undefined if
+C<mbrtowc> was substituted, so you should never rely on it.
+
+When the second parameter is a scalar containing a value that either is
+a PV string or can be forced into one, the return value is the number of
+bytes occupied by the first character of that string; or 0 if that first
+character is the wide NUL character; or negative if there is an error.
+This is based on the locale that currently underlies the program,
+regardless of whether or not the function is called from Perl code that
+is within the scope of S<C<use locale>>.  Perl makes no attempt at
+hiding from your code any differences in the C<errno> setting between
+C<mbtowc> and C<mbrtowc>.  It does set C<errno> to 0 before calling
+them.

 
 =item C<memchr>
 
 
 =item C<memchr>
 


@@ -1120,7 +1222,7 @@ See also L</nan>, C</isnan>, and L</fpclassify>.
 
    my $nan = nan();
 
 
    my $nan = nan();
 

-Returns C<NaN>, not-a-number [C99].
+Returns C<NaN>, not-a-number [C99].  Added in Perl v5.22.

 
 The returned NaN is always a I<quiet> NaN, as opposed to I<signaling>.
 
 
 The returned NaN is always a I<quiet> NaN, as opposed to I<signaling>.
 


@@ -1156,12 +1258,12 @@ See also L</isnan>, L</NaN>, L</setpayload> and L</issignaling>.
 =item C<nearbyint>
 
 Returns the nearest integer to the argument, according to the current
 =item C<nearbyint>
 
 Returns the nearest integer to the argument, according to the current

-rounding mode (see L</fegetround>) [C99].
+rounding mode (see L</fegetround>) [C99].  Added in Perl v5.22.

 
 =item C<nextafter>
 
 Returns the next representable floating point number after C<x> in the
 
 =item C<nextafter>
 
 Returns the next representable floating point number after C<x> in the

-direction of C<y> [C99].
+direction of C<y> [C99].  Added in Perl v5.22.

 
  my $nextafter = POSIX::nextafter($x, $y);
 
 
  my $nextafter = POSIX::nextafter($x, $y);
 


@@ -1170,7 +1272,7 @@ Like L</nexttoward>, but potentially less accurate.
 =item C<nexttoward>
 
 Returns the next representable floating point number after C<x> in the
 =item C<nexttoward>
 
 Returns the next representable floating point number after C<x> in the

-direction of C<y> [C99].
+direction of C<y> [C99].  Added in Perl v5.22.

 
  my $nexttoward = POSIX::nexttoward($x, $y);
 
 
  my $nexttoward = POSIX::nexttoward($x, $y);
 


@@ -1329,7 +1431,7 @@ Not implemented.  C<realloc()> is C-specific.  Perl does memory management trans
 =item C<remainder>
 
 Given C<x> and C<y>, returns the value S<C<x - n*y>>, where C<n> is the integer
 =item C<remainder>
 
 Given C<x> and C<y>, returns the value S<C<x - n*y>>, where C<n> is the integer

-closest to C<x>/C<y>. [C99]
+closest to C<x>/C<y> [C99].  Added in Perl v5.22.

 
  my $remainder = POSIX::remainder($x, $y)
 
 
  my $remainder = POSIX::remainder($x, $y)
 


@@ -1337,13 +1439,13 @@ See also L</remquo>.
 
 =item C<remove>
 
 
 =item C<remove>
 

-This is identical to Perl's builtin C<unlink()> function
-for removing files, see L<perlfunc/unlink>.
+Deletes a name from the filesystem.  Calls L<perlfunc/unlink> for
+files and L<perlfunc/rmdir> for directories.

 
 =item C<remquo>
 
 Like L</remainder> but also returns the low-order bits of the quotient (n)
 
 =item C<remquo>
 
 Like L</remainder> but also returns the low-order bits of the quotient (n)

-[C99]
+[C99].  Added in Perl v5.22.

 
 (This is quite esoteric interface, mainly used to implement numerical
 algorithms.)
 
 (This is quite esoteric interface, mainly used to implement numerical
 algorithms.)


@@ -1374,13 +1476,13 @@ for removing (empty) directories, see L<perlfunc/rmdir>.
 =item C<round>
 
 Returns the integer (but still as floating point) nearest to the
 =item C<round>
 
 Returns the integer (but still as floating point) nearest to the

-argument [C99].
+argument [C99].  Added in Perl v5.22.

 
 See also L</ceil>, L</floor>, L</lround>, L</modf>, and L</trunc>.
 
 =item C<scalbn>
 
 
 See also L</ceil>, L</floor>, L</lround>, L</modf>, and L</trunc>.
 
 =item C<scalbn>
 

-Returns S<C<x * 2**y>> [C99].
+Returns S<C<x * 2**y>> [C99].  Added in Perl v5.22.

 
 See also L</frexp> and L</ldexp>.
 
 
 See also L</frexp> and L</ldexp>.
 


@@ -1405,14 +1507,19 @@ see L<perlfunc/eval>.
 
 =item C<setlocale>
 
 
 =item C<setlocale>
 

-WARNING!  Do NOT use this function in a L<thread|threads>.  The locale
-will change in all other threads at the same time, and should your
-thread get paused by the operating system, and another started, that
-thread will not have the locale it is expecting.  On some platforms,
-there can be a race leading to segfaults if two threads call this
-function nearly simultaneously.
-
-Modifies and queries the program's underlying locale.  Users of this
+WARNING!  Prior to Perl 5.28 or on a system that does not support
+thread-safe locale operations, do NOT use this function in a
+L<thread|threads>.  The locale will change in all other threads at the
+same time, and should your thread get paused by the operating system,
+and another started, that thread will not have the locale it is
+expecting.  On some platforms, there can be a race leading to segfaults
+if two threads call this function nearly simultaneously.  This warning
+does not apply on unthreaded builds, or on perls where
+C<${^SAFE_LOCALES}> exists and is non-zero; namely Perl 5.28 and later
+compiled to be locale-thread-safe.
+
+This function
+modifies and queries the program's underlying locale.  Users of this

 function should read L<perllocale>, whch provides a comprehensive
 discussion of Perl locale handling, knowledge of which is necessary to
 properly use this function.  It contains
 function should read L<perllocale>, whch provides a comprehensive
 discussion of Perl locale handling, knowledge of which is necessary to
 properly use this function.  It contains


@@ -1420,7 +1527,9 @@ L<a section devoted to this function|perllocale/The setlocale function>.
 The discussion here is merely a summary reference for C<setlocale()>.
 Note that Perl itself is almost entirely unaffected by the locale
 except within the scope of S<C<"use locale">>.  (Exceptions are listed
 The discussion here is merely a summary reference for C<setlocale()>.
 Note that Perl itself is almost entirely unaffected by the locale
 except within the scope of S<C<"use locale">>.  (Exceptions are listed

-in L<perllocale/Not within the scope of "use locale">.)
+in L<perllocale/Not within the scope of "use locale">, and
+locale-dependent functions within the POSIX module ARE always affected
+by the current locale.)

 
 The following examples assume
 
 
 The following examples assume
 


@@ -1457,7 +1566,7 @@ out which locales are available in your system.
        use POSIX ':nan_payload';
        setpayload($var, $payload);
 
        use POSIX ':nan_payload';
        setpayload($var, $payload);
 

-Sets the C<NaN> payload of var.
+Sets the C<NaN> payload of var.  Added in Perl v5.24.

 
 NOTE: the NaN payload APIs are based on the latest (as of June 2015)
 proposed ISO C interfaces, but they are not yet a standard.  Things
 
 NOTE: the NaN payload APIs are based on the latest (as of June 2015)
 proposed ISO C interfaces, but they are not yet a standard.  Things


@@ -1472,7 +1581,8 @@ See also L</setpayloadsig>, L</isnan>, L</getpayload>, and L</issignaling>.
        use POSIX ':nan_payload';
        setpayloadsig($var, $payload);
 
        use POSIX ':nan_payload';
        setpayloadsig($var, $payload);
 

-Like L</setpayload> but also makes the NaN I<signaling>.
+Like L</setpayload> but also makes the NaN I<signaling>.  Added in Perl
+v5.24.

 
 Depending on the platform the NaN may or may not behave differently.
 
 
 Depending on the platform the NaN may or may not behave differently.
 


@@ -1530,7 +1640,7 @@ semantics, as defined by POSIX/SUSv3:
                 otherwise the signal was sent by the kernel
 
 The constants for specific C<code> values can be imported individually
                 otherwise the signal was sent by the kernel
 
 The constants for specific C<code> values can be imported individually

-or using the C<:signal_h_si_code> tag.
+or using the C<:signal_h_si_code> tag, since Perl v5.24.

 
 The following are also defined by POSIX/SUSv3, but unfortunately
 not very widely implemented:
 
 The following are also defined by POSIX/SUSv3, but unfortunately
 not very widely implemented:


@@ -1559,6 +1669,7 @@ Not implemented.  C<siglongjmp()> is C-specific: use L<perlfunc/die> instead.
 =item C<signbit>
 
 Returns zero for positive arguments, non-zero for negative arguments [C99].
 =item C<signbit>
 
 Returns zero for positive arguments, non-zero for negative arguments [C99].

+Added in Perl v5.22.

 
 =item C<sigpending>
 
 
 =item C<sigpending>
 


@@ -1770,9 +1881,13 @@ POSIX-compliant systems set C<$!> (C<$ERRNO>) to indicate a translation
 error, so clear C<$!> before calling C<strtod>.  However, non-POSIX systems
 may not check for overflow, and therefore will never set C<$!>.
 
 error, so clear C<$!> before calling C<strtod>.  However, non-POSIX systems
 may not check for overflow, and therefore will never set C<$!>.
 

-C<strtod> respects any POSIX C<setlocale()> C<LC_TIME> settings,
+C<strtod> respects any POSIX C<setlocale()> C<LC_NUMERIC> settings,

 regardless of whether or not it is called from Perl code that is within
 regardless of whether or not it is called from Perl code that is within

-the scope of S<C<use locale>>.
+the scope of S<C<use locale>>.  Prior to Perl 5.28, or when operating in
+a non thread-safe environment, it should not be used in a threaded
+application unless it's certain that the underlying locale is C
+or POSIX.  This is because it otherwise changes the locale, which
+globally affects all threads simultaneously.

 
 To parse a string C<$str> as a floating point number use
 
 
 To parse a string C<$str> as a floating point number use
 


@@ -1920,7 +2035,7 @@ Returns C<undef> on failure.
 
 =item C<tgamma>
 
 
 =item C<tgamma>
 

-The Gamma function [C99].
+The Gamma function [C99].  Added in Perl v5.22.

 
 See also L</lgamma>.
 
 
 See also L</lgamma>.
 


@@ -1951,10 +2066,11 @@ Not implemented.  Use method C<IO::File::new_tmpfile()> instead, or see L<File::
 
 For security reasons, which are probably detailed in your system's
 documentation for the C library C<tmpnam()> function, this interface
 
 For security reasons, which are probably detailed in your system's
 documentation for the C library C<tmpnam()> function, this interface

-is no longer available; instead use L<File::Temp>.
+is no longer available since Perl v5.26; instead use L<File::Temp>.

 
 =item C<tolower>
 
 
 =item C<tolower>
 

+This function has been removed as of Perl v5.26.

 This is identical to the C function, except that it can apply to a single
 character or to a whole string, and currently operates as if the locale
 always is "C".  Consider using the C<lc()> function, see L<perlfunc/lc>,
 This is identical to the C function, except that it can apply to a single
 character or to a whole string, and currently operates as if the locale
 always is "C".  Consider using the C<lc()> function, see L<perlfunc/lc>,


@@ -1963,6 +2079,7 @@ strings.
 
 =item C<toupper>
 
 
 =item C<toupper>
 

+This function has been removed as of Perl v5.26.

 This is similar to the C function, except that it can apply to a single
 character or to a whole string, and currently operates as if the locale
 always is "C".  Consider using the C<uc()> function, see L<perlfunc/uc>,
 This is similar to the C function, except that it can apply to a single
 character or to a whole string, and currently operates as if the locale
 always is "C".  Consider using the C<uc()> function, see L<perlfunc/uc>,


@@ -1970,7 +2087,8 @@ or the equivalent C<\U> operator inside doublequotish strings.
 
 =item C<trunc>
 
 
 =item C<trunc>
 

-Returns the integer toward zero from the argument [C99].
+Returns the integer toward zero from the argument [C99].  Added in Perl
+v5.22.

 
 See also L</ceil>, L</floor>, and L</round>.
 
 
 See also L</ceil>, L</floor>, and L</round>.
 


@@ -2055,17 +2173,34 @@ builtin C<waitpid()> function, see L<perlfunc/waitpid>.
        $pid = POSIX::waitpid( -1, POSIX::WNOHANG );
        print "status = ", ($? / 256), "\n";
 
        $pid = POSIX::waitpid( -1, POSIX::WNOHANG );
        print "status = ", ($? / 256), "\n";
 

-=item C<wcstombs>
-
-This is identical to the C function C<wcstombs()>.
-

 See L</mblen>.
 
 =item C<wctomb>
 
 See L</mblen>.
 
 =item C<wctomb>
 

-This is identical to the C function C<wctomb()>.
-
-See L</mblen>.
+This is the same as the C function C<wctomb()> on unthreaded perls.  On
+threaded perls, it transparently (almost) substitutes the more
+thread-safe L<C<wcrtomb>(3)>, if available, instead of C<wctomb>.
+
+Core Perl does not have any support for wide and multibyte locales,
+except Unicode UTF-8 locales.  This function, in conjunction with
+L</mblen> and L</mbtowc> may be used to roll your own decoding/encoding
+of other types of multi-byte locales.
+
+Use C<undef> as the first parameter to this function to get the effect
+of passing NULL as the first parameter to C<wctomb>.  This resets any
+shift state to its initial value.  The return value is undefined if
+C<wcrtomb> was substituted, so you should never rely on it.
+
+When the first parameter is a scalar, the code point contained in the
+scalar second parameter is converted into a multi-byte string and stored
+into the first parameter scalar.  This is based on the locale that
+currently underlies the program, regardless of whether or not the
+function is called from Perl code that is within the scope of S<C<use
+locale>>.  The return value is the number of bytes stored; or negative
+if the code point isn't representable in the current locale.  Perl makes
+no attempt at hiding from your code any differences in the C<errno>
+setting between C<wctomb> and C<wcrtomb>.  It does set C<errno> to 0
+before calling them.

 
 =item C<write>
 
 
 =item C<write>
 


@@ -2208,6 +2343,9 @@ Create a set with C<SIGUSR1>.
 
        $sigset = POSIX::SigSet->new( &POSIX::SIGUSR1 );
 
 
        $sigset = POSIX::SigSet->new( &POSIX::SIGUSR1 );
 

+Throws an error if any of the signals supplied cannot be added to the
+set.
+

 =item C<addset>
 
 Add a signal to a SigSet object.
 =item C<addset>
 
 Add a signal to a SigSet object.


@@ -2433,6 +2571,20 @@ C<_POSIX_TZNAME_MAX> C<_POSIX_VDISABLE> C<_POSIX_VERSION>
 
 =back
 
 
 =back
 

+=head1 RESOURCE CONSTANTS
+
+Imported with the C<:sys_resource_h> tag.
+
+=over 8
+
+=item Constants
+
+Added in Perl v5.28:
+
+C<PRIO_PROCESS> C<PRIO_PGRP> C<PRIO_USER>
+
+=back
+

 =head1 SYSTEM CONFIGURATION
 
 =over 8
 =head1 SYSTEM CONFIGURATION
 
 =over 8


@@ -2534,6 +2686,8 @@ on systems that support them.
 
 C<HUGE_VAL>
 
 
 C<HUGE_VAL>
 

+Added in Perl v5.22:
+

 C<FP_ILOGB0> C<FP_ILOGBNAN> C<FP_INFINITE> C<FP_NAN> C<FP_NORMAL> C<FP_SUBNORMAL> C<FP_ZERO>
 C<INFINITY> C<NAN> C<Inf> C<NaN>
 C<M_1_PI> C<M_2_PI> C<M_2_SQRTPI> C<M_E> C<M_LN10> C<M_LN2> C<M_LOG10E> C<M_LOG2E> C<M_PI>
 C<FP_ILOGB0> C<FP_ILOGBNAN> C<FP_INFINITE> C<FP_NAN> C<FP_NORMAL> C<FP_SUBNORMAL> C<FP_ZERO>
 C<INFINITY> C<NAN> C<Inf> C<NaN>
 C<M_1_PI> C<M_2_PI> C<M_2_SQRTPI> C<M_E> C<M_LN10> C<M_LN2> C<M_LOG10E> C<M_LOG2E> C<M_PI>


@@ -2553,6 +2707,9 @@ C<SA_SIGINFO> C<SIGABRT> C<SIGALRM> C<SIGCHLD> C<SIGCONT> C<SIGFPE> C<SIGHUP> C<
 C<SIGKILL> C<SIGPIPE> C<SIGQUIT> C<SIGSEGV> C<SIGSTOP> C<SIGTERM> C<SIGTSTP> C<SIGTTIN> C<SIGTTOU>
 C<SIGUSR1> C<SIGUSR2> C<SIG_BLOCK> C<SIG_DFL> C<SIG_ERR> C<SIG_IGN> C<SIG_SETMASK>
 C<SIG_UNBLOCK>
 C<SIGKILL> C<SIGPIPE> C<SIGQUIT> C<SIGSEGV> C<SIGSTOP> C<SIGTERM> C<SIGTSTP> C<SIGTTIN> C<SIGTTOU>
 C<SIGUSR1> C<SIGUSR2> C<SIG_BLOCK> C<SIG_DFL> C<SIG_ERR> C<SIG_IGN> C<SIG_SETMASK>
 C<SIG_UNBLOCK>

+
+Added in Perl v5.24:
+

 C<ILL_ILLOPC> C<ILL_ILLOPN> C<ILL_ILLADR> C<ILL_ILLTRP> C<ILL_PRVOPC> C<ILL_PRVREG> C<ILL_COPROC>
 C<ILL_BADSTK> C<FPE_INTDIV> C<FPE_INTOVF> C<FPE_FLTDIV> C<FPE_FLTOVF> C<FPE_FLTUND> C<FPE_FLTRES>
 C<FPE_FLTINV> C<FPE_FLTSUB> C<SEGV_MAPERR> C<SEGV_ACCERR> C<BUS_ADRALN> C<BUS_ADRERR>
 C<ILL_ILLOPC> C<ILL_ILLOPN> C<ILL_ILLADR> C<ILL_ILLTRP> C<ILL_PRVOPC> C<ILL_PRVREG> C<ILL_COPROC>
 C<ILL_BADSTK> C<FPE_INTDIV> C<FPE_INTOVF> C<FPE_FLTDIV> C<FPE_FLTOVF> C<FPE_FLTUND> C<FPE_FLTRES>
 C<FPE_FLTINV> C<FPE_FLTSUB> C<SEGV_MAPERR> C<SEGV_ACCERR> C<BUS_ADRALN> C<BUS_ADRERR>


@@ -2692,6 +2849,8 @@ is true)
 
 =item Constants
 
 
 =item Constants
 

+Added in Perl v5.24:
+

 C<WSAEINTR> C<WSAEBADF> C<WSAEACCES> C<WSAEFAULT> C<WSAEINVAL> C<WSAEMFILE> C<WSAEWOULDBLOCK>
 C<WSAEINPROGRESS> C<WSAEALREADY> C<WSAENOTSOCK> C<WSAEDESTADDRREQ> C<WSAEMSGSIZE>
 C<WSAEPROTOTYPE> C<WSAENOPROTOOPT> C<WSAEPROTONOSUPPORT> C<WSAESOCKTNOSUPPORT>
 C<WSAEINTR> C<WSAEBADF> C<WSAEACCES> C<WSAEFAULT> C<WSAEINVAL> C<WSAEMFILE> C<WSAEWOULDBLOCK>
 C<WSAEINPROGRESS> C<WSAEALREADY> C<WSAENOTSOCK> C<WSAEDESTADDRREQ> C<WSAEMSGSIZE>
 C<WSAEPROTOTYPE> C<WSAENOPROTOOPT> C<WSAEPROTONOSUPPORT> C<WSAESOCKTNOSUPPORT>