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NAME

       POSIX - Perl interface to IEEE Std 1003.1

SYNOPSIS

           use POSIX ();
           use POSIX qw(setsid);
           use POSIX qw(:errno_h :fcntl_h);

           printf "EINTR is %d\n", EINTR;

           $sess_id = POSIX::setsid();

           $fd = POSIX::open($path, O_CREAT|O_EXCL|O_WRONLY, 0644);
               # note: that's a filedescriptor, *NOT* a filehandle

DESCRIPTION

       The POSIX module permits you to access all (or nearly all) the standard POSIX 1003.1
       identifiers.  Many of these identifiers have been given Perl-ish 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 perlfunc for functions which are noted as being 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, and other miscellaneous
       objects.  The remaining sections list various constants and macros in an organization
       which roughly follows IEEE Std 1003.1b-1993.

CAVEATS

       Everything is exported by default (with a handful of exceptions).  This is an unfortunate
       backwards compatibility feature and its use is strongly discouraged.  You should either
       prevent the exporting (by saying "use POSIX ();", as usual) and then use fully qualified
       names (e.g. "POSIX::SEEK_END"), or give an explicit import list.  If you do neither and
       opt for the default (as in "use POSIX;"), you will import hundreds and hundreds of symbols
       into your namespace.

       A few functions are not implemented because they are C specific.  If you attempt to call
       these, they will print a message telling you that they aren't implemented, and suggest
       using the Perl equivalent, should one exist.  For example, trying to access the "setjmp()"
       call will elicit the message ""setjmp() is C-specific: use eval {} instead"".

       Furthermore, some evil vendors will claim 1003.1 compliance, but in fact are not so: they
       will not pass the PCTS (POSIX Compliance Test Suites).  For example, one vendor may not
       define "EDEADLK", or the semantics of the errno values set by open(2) might not be quite
       right.  Perl does not attempt to verify POSIX compliance.  That means you can currently
       successfully say "use POSIX",  and then later in your program you find that your vendor
       has been lax and there's no usable "ICANON" macro after all.  This could be construed to
       be a bug.

FUNCTIONS

       "_exit" This is identical to the C function "_exit()".  It exits the program immediately
               which means among other things buffered I/O is not flushed.

               Note that when using threads and in Linux this is not a good way to exit a thread
               because in Linux processes and threads are kind of the same thing (Note: while
               this is the situation in early 2003 there are projects under way to have threads
               with more POSIXly semantics in Linux).  If you want not to return from a thread,
               detach the thread.

       "abort" This is identical to the C function "abort()".  It terminates the process with a
               "SIGABRT" signal unless caught by a signal handler or if the handler does not
               return normally (it e.g.  does a "longjmp").

       "abs"   This is identical to Perl's builtin "abs()" function, returning the absolute value
               of its numerical argument (except that "POSIX::abs()" must be provided an explicit
               value (rather than relying on an implicit $_):

                   $absolute_value = POSIX::abs(42);   # good

                   $absolute_value = POSIX::abs();     # throws exception

       "access"
               Determines the accessibility of a file.

                       if( POSIX::access( "/", &POSIX::R_OK ) ){
                               print "have read permission\n";
                       }

               Returns "undef" on failure.  Note: do not use "access()" for security purposes.
               Between the "access()" call and the operation you are preparing for the
               permissions might change: a classic race condition.

       "acos"  This is identical to the C function "acos()", returning the arcus cosine of its
               numerical argument.  See also Math::Trig.

       "acosh" This is identical to the C function "acosh()", returning the hyperbolic arcus
               cosine of its numerical argument [C99].  See also Math::Trig.

       "alarm" This is identical to Perl's builtin "alarm()" function, either for arming or
               disarming the "SIGARLM" timer, except that "POSIX::alarm()" must be provided an
               explicit value (rather than relying on an implicit $_):

                   POSIX::alarm(3)     # good

                   POSIX::alarm()      # throws exception

       "asctime"
               This is identical to the C function "asctime()".  It returns a string of the form

                       "Fri Jun  2 18:22:13 2000\n\0"

               and it is called thusly

                       $asctime = asctime($sec, $min, $hour, $mday, $mon,
                                          $year, $wday, $yday, $isdst);

               The $mon is zero-based: January equals 0.  The $year is 1900-based: 2001 equals
               101.  $wday and $yday default to zero (and are usually ignored anyway), and $isdst
               defaults to -1.

       "asin"  This is identical to the C function "asin()", returning the arcus sine of its
               numerical argument.  See also Math::Trig.

       "asinh" This is identical to the C function "asinh()", returning the hyperbolic arcus sine
               of its numerical argument [C99].  See also Math::Trig.

       "assert"
               Unimplemented, but you can use "die" in perlfunc and the Carp module to achieve
               similar things.

       "atan"  This is identical to the C function "atan()", returning the arcus tangent of its
               numerical argument.  See also Math::Trig.

       "atanh" This is identical to the C function "atanh()", returning the hyperbolic arcus
               tangent of its numerical argument [C99].  See also Math::Trig.

       "atan2" This is identical to Perl's builtin "atan2()" function, returning the arcus
               tangent defined by its two numerical arguments, the y coordinate and the x
               coordinate.  See also Math::Trig.

       "atexit"
               Not implemented.  "atexit()" is C-specific: use "END {}" instead, see perlmod.

       "atof"  Not implemented.  "atof()" is C-specific.  Perl converts strings to numbers
               transparently.  If you need to force a scalar to a number, add a zero to it.

       "atoi"  Not implemented.  "atoi()" is C-specific.  Perl converts strings to numbers
               transparently.  If you need to force a scalar to a number, add a zero to it.  If
               you need to have just the integer part, see "int" in perlfunc.

       "atol"  Not implemented.  "atol()" is C-specific.  Perl converts strings to numbers
               transparently.  If you need to force a scalar to a number, add a zero to it.  If
               you need to have just the integer part, see "int" in perlfunc.

       "bsearch"
               "bsearch()" not supplied.  For doing binary search on wordlists, see Search::Dict.

       "calloc"
               Not implemented.  "calloc()" is C-specific.  Perl does memory management
               transparently.

       "cbrt"  The cube root [C99].

       "ceil"  This is identical to the C function "ceil()", returning the smallest integer value
               greater than or equal to the given numerical argument.

       "chdir" This is identical to Perl's builtin "chdir()" function, allowing one to change the
               working (default) directory -- see "chdir" in perlfunc -- with the exception that
               "POSIX::chdir()" must be provided an explicit value (rather than relying on an
               implicit $_):

                   $rv = POSIX::chdir('path/to/dir');      # good

                   $rv = POSIX::chdir();                   # throws exception

       "chmod" This is identical to Perl's builtin "chmod()" function, allowing one to change
               file and directory permissions -- see "chmod" in perlfunc -- with the exception
               that "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 "chmod()", $file may be a filename or a file handle.

       "chown" This is identical to Perl's builtin "chown()" function, allowing one to change
               file and directory owners and groups, see "chown" in perlfunc.

       "clearerr"
               Not implemented.  Use the method "IO::Handle::clearerr()" instead, to reset the
               error state (if any) and EOF state (if any) of the given stream.

       "clock" This is identical to the C function "clock()", returning the amount of spent
               processor time in microseconds.

       "close" Close the file.  This uses file descriptors such as those obtained by calling
               "POSIX::open".

                       $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
                       POSIX::close( $fd );

               Returns "undef" on failure.

               See also "close" in perlfunc.

       "closedir"
               This is identical to Perl's builtin "closedir()" function for closing a directory
               handle, see "closedir" in perlfunc.

       "cos"   This is identical to Perl's builtin "cos()" function, for returning the cosine of
               its numerical argument, see "cos" in perlfunc.  See also Math::Trig.

       "cosh"  This is identical to the C function "cosh()", for returning the hyperbolic cosine
               of its numeric argument.  See also Math::Trig.

       "copysign"
               Returns "x" but with the sign of "y" [C99].

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

               See also "signbit".

       "creat" Create a new file.  This returns a file descriptor like the ones returned by
               "POSIX::open".  Use "POSIX::close" to close the file.

                       $fd = POSIX::creat( "foo", 0611 );
                       POSIX::close( $fd );

               See also "sysopen" in perlfunc and its "O_CREAT" flag.

       "ctermid"
               Generates the path name for the controlling terminal.

                       $path = POSIX::ctermid();

       "ctime" This is identical to the C function "ctime()" and equivalent to
               "asctime(localtime(...))", see "asctime" and "localtime".

       "cuserid" [POSIX.1-1988]
               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 "getlogin()" instead.

       "difftime"
               This is identical to the C function "difftime()", for returning the time
               difference (in seconds) between two times (as returned by "time()"), see "time".

       "div"   Not implemented.  "div()" is C-specific, use "int" in perlfunc on the usual "/"
               division and the modulus "%".

       "dup"   This is similar to the C function "dup()", for duplicating a file descriptor.

               This uses file descriptors such as those obtained by calling "POSIX::open".

               Returns "undef" on failure.

       "dup2"  This is similar to the C function "dup2()", for duplicating a file descriptor to
               an another known file descriptor.

               This uses file descriptors such as those obtained by calling "POSIX::open".

               Returns "undef" on failure.

       "erf"   The error function [C99].

       "erfc"  The complementary error function [C99].

       "errno" Returns the value of errno.

                       $errno = POSIX::errno();

               This identical to the numerical values of the $!, see "$ERRNO" in perlvar.

       "execl" Not implemented.  "execl()" is C-specific, see "exec" in perlfunc.

       "execle"
               Not implemented.  "execle()" is C-specific, see "exec" in perlfunc.

       "execlp"
               Not implemented.  "execlp()" is C-specific, see "exec" in perlfunc.

       "execv" Not implemented.  "execv()" is C-specific, see "exec" in perlfunc.

       "execve"
               Not implemented.  "execve()" is C-specific, see "exec" in perlfunc.

       "execvp"
               Not implemented.  "execvp()" is C-specific, see "exec" in perlfunc.

       "exit"  This is identical to Perl's builtin "exit()" function for exiting the program, see
               "exit" in perlfunc.

       "exp"   This is identical to Perl's builtin "exp()" function for returning the exponent
               (e-based) of the numerical argument, see "exp" in perlfunc.

       "expm1" Equivalent to "exp(x) - 1", but more precise for small argument values [C99].

               See also "log1p".

       "fabs"  This is identical to Perl's builtin "abs()" function for returning the absolute
               value of the numerical argument, see "abs" in perlfunc.

       "fclose"
               Not implemented.  Use method "IO::Handle::close()" instead, or see "close" in
               perlfunc.

       "fcntl" This is identical to Perl's builtin "fcntl()" function, see "fcntl" in perlfunc.

       "fdopen"
               Not implemented.  Use method "IO::Handle::new_from_fd()" instead, or see "open" in
               perlfunc.

       "feof"  Not implemented.  Use method "IO::Handle::eof()" instead, or see "eof" in
               perlfunc.

       "ferror"
               Not implemented.  Use method "IO::Handle::error()" instead.

       "fflush"
               Not implemented.  Use method "IO::Handle::flush()" instead.  See also
               ""$OUTPUT_AUTOFLUSH" in perlvar".

       "fgetc" Not implemented.  Use method "IO::Handle::getc()" instead, or see "read" in
               perlfunc.

       "fgetpos"
               Not implemented.  Use method "IO::Seekable::getpos()" instead, or see "seek" in
               perlfunc.

       "fgets" Not implemented.  Use method "IO::Handle::gets()" instead.  Similar to <>, also
               known as "readline" in perlfunc.

       "fileno"
               Not implemented.  Use method "IO::Handle::fileno()" instead, or see "fileno" in
               perlfunc.

       "floor" This is identical to the C function "floor()", returning the largest integer value
               less than or equal to the numerical argument.

       "fdim"  "Positive difference", "x - y" if "x > y", zero otherwise [C99].

       "fegetround"
               Returns the current floating point rounding mode, one of

                 FE_TONEAREST FE_TOWARDZERO FE_UPWARD FE_UPWARD

               "FE_TONEAREST" is like "round", "FE_TOWARDZERO" is like "trunc" [C99].

       "fesetround"
               Sets the floating point rounding mode, see "fegetround" [C99].

       "fma"   "Fused multiply-add", "x * y + z", possibly faster (and less lossy) than the
               explicit two operations [C99].

                my $fused = POSIX::fma($x, $y, $z);

       "fmax"  Maximum of "x" and "y", except when either is "NaN", returns the other [C99].

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

       "fmin"  Minimum of "x" and "y", except when either is "NaN", returns the other [C99].

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

       "fmod"  This is identical to the C function "fmod()".

                       $r = fmod($x, $y);

               It returns the remainder "$r = $x - $n*$y", where "$n = trunc($x/$y)".  The $r has
               the same sign as $x and magnitude (absolute value) less than the magnitude of $y.

       "fopen" Not implemented.  Use method "IO::File::open()" instead, or see "open" in
               perlfunc.

       "fork"  This is identical to Perl's builtin "fork()" function for duplicating the current
               process, see "fork" in perlfunc and perlfork if you are in Windows.

       "fpathconf"
               Retrieves the value of a configurable limit on a file or directory.  This uses
               file descriptors such as those obtained by calling "POSIX::open".

               The following will determine the maximum length of the longest allowable pathname
               on the filesystem which holds /var/foo.

                       $fd = POSIX::open( "/var/foo", &POSIX::O_RDONLY );
                       $path_max = POSIX::fpathconf($fd, &POSIX::_PC_PATH_MAX);

               Returns "undef" on failure.

       "fpclassify"
               Returns one of

                 FP_NORMAL FP_ZERO FP_SUBNORMAL FP_INFINITE FP_NAN

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

       "fprintf"
               Not implemented.  "fprintf()" is C-specific, see "printf" in perlfunc instead.

       "fputc" Not implemented.  "fputc()" is C-specific, see "print" in perlfunc instead.

       "fputs" Not implemented.  "fputs()" is C-specific, see "print" in perlfunc instead.

       "fread" Not implemented.  "fread()" is C-specific, see "read" in perlfunc instead.

       "free"  Not implemented.  "free()" is C-specific.  Perl does memory management
               transparently.

       "freopen"
               Not implemented.  "freopen()" is C-specific, see "open" in perlfunc instead.

       "frexp" Return the mantissa and exponent of a floating-point number.

                       ($mantissa, $exponent) = POSIX::frexp( 1.234e56 );

       "fscanf"
               Not implemented.  "fscanf()" is C-specific, use <> and regular expressions
               instead.

       "fseek" Not implemented.  Use method "IO::Seekable::seek()" instead, or see "seek" in
               perlfunc.

       "fsetpos"
               Not implemented.  Use method "IO::Seekable::setpos()" instead, or seek "seek" in
               perlfunc.

       "fstat" Get file status.  This uses file descriptors such as those obtained by calling
               "POSIX::open".  The data returned is identical to the data from Perl's builtin
               "stat" function.

                       $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
                       @stats = POSIX::fstat( $fd );

       "fsync" Not implemented.  Use method "IO::Handle::sync()" instead.

       "ftell" Not implemented.  Use method "IO::Seekable::tell()" instead, or see "tell" in
               perlfunc.

       "fwrite"
               Not implemented.  "fwrite()" is C-specific, see "print" in perlfunc instead.

       "getc"  This is identical to Perl's builtin "getc()" function, see "getc" in perlfunc.

       "getchar"
               Returns one character from STDIN.  Identical to Perl's "getc()", see "getc" in
               perlfunc.

       "getcwd"
               Returns the name of the current working directory.  See also Cwd.

       "getegid"
               Returns the effective group identifier.  Similar to Perl' s builtin variable $(,
               see "$EGID" in perlvar.

       "getenv"
               Returns the value of the specified environment variable.  The same information is
               available through the %ENV array.

       "geteuid"
               Returns the effective user identifier.  Identical to Perl's builtin $> variable,
               see "$EUID" in perlvar.

       "getgid"
               Returns the user's real group identifier.  Similar to Perl's builtin variable $),
               see "$GID" in perlvar.

       "getgrgid"
               This is identical to Perl's builtin "getgrgid()" function for returning group
               entries by group identifiers, see "getgrgid" in perlfunc.

       "getgrnam"
               This is identical to Perl's builtin "getgrnam()" function for returning group
               entries by group names, see "getgrnam" in perlfunc.

       "getgroups"
               Returns the ids of the user's supplementary groups.  Similar to Perl's builtin
               variable $), see "$GID" in perlvar.

       "getlogin"
               This is identical to Perl's builtin "getlogin()" function for returning the user
               name associated with the current session, see "getlogin" in perlfunc.

       "getpayload"
                       use POSIX ':nan_payload';
                       getpayload($var)

               Returns the "NaN" payload.

               Note the API instability warning in "setpayload".

               See "nan" for more discussion about "NaN".

       "getpgrp"
               This is identical to Perl's builtin "getpgrp()" function for returning the process
               group identifier of the current process, see "getpgrp" in perlfunc.

       "getpid"
               Returns the process identifier.  Identical to Perl's builtin variable $$, see
               "$PID" in perlvar.

       "getppid"
               This is identical to Perl's builtin "getppid()" function for returning the process
               identifier of the parent process of the current process , see "getppid" in
               perlfunc.

       "getpwnam"
               This is identical to Perl's builtin "getpwnam()" function for returning user
               entries by user names, see "getpwnam" in perlfunc.

       "getpwuid"
               This is identical to Perl's builtin "getpwuid()" function for returning user
               entries by user identifiers, see "getpwuid" in perlfunc.

       "gets"  Returns one line from "STDIN", similar to <>, also known as the "readline()"
               function, see "readline" in perlfunc.

               NOTE: if you have C programs that still use "gets()", be very afraid.  The
               "gets()" function is a source of endless grief because it has no buffer overrun
               checks.  It should never be used.  The "fgets()" function should be preferred
               instead.

       "getuid"
               Returns the user's identifier.  Identical to Perl's builtin $< variable, see
               "$UID" in perlvar.

       "gmtime"
               This is identical to Perl's builtin "gmtime()" function for converting seconds
               since the epoch to a date in Greenwich Mean Time, see "gmtime" in perlfunc.

       "hypot" Equivalent to "sqrt(x * x + y * y)" except more stable on very large or very small
               arguments [C99].

       "ilogb" Integer binary logarithm [C99]

               For example "ilogb(20)" is 4, as an integer.

               See also "logb".

       "Inf"   The infinity as a constant:

                  use POSIX qw(Inf);
                  my $pos_inf = +Inf;  # Or just Inf.
                  my $neg_inf = -Inf;

               See also "isinf", and "fpclassify".

       "isalnum"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:alnum:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "isalpha"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:alpha:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "isatty"
               Returns a boolean indicating whether the specified filehandle is connected to a
               tty.  Similar to the "-t" operator, see "-X" in perlfunc.

       "iscntrl"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:cntrl:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "isdigit"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:digit:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "isfinite"
               Returns true if the argument is a finite number (that is, not an infinity, or the
               not-a-number) [C99].

               See also "isinf", "isnan", and "fpclassify".

       "isgraph"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:graph:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "isgreater"
               (Also "isgreaterequal", "isless", "islessequal", "islessgreater", "isunordered")

               Floating point comparisons which handle the "NaN" [C99].

       "isinf" Returns true if the argument is an infinity (positive or negative) [C99].

               See also "Inf", "isnan", "isfinite", and "fpclassify".

       "islower"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:lower:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "isnan" Returns true if the argument is "NaN" (not-a-number) [C99].

               Note that you cannot test for ""NaN"-ness" with

                  $x == $x

               since the "NaN" is not equivalent to anything, including itself.

               See also "nan", "NaN", "isinf", and "fpclassify".

       "isnormal"
               Returns true if the argument is normal (that is, not a subnormal/denormal, and not
               an infinity, or a not-a-number) [C99].

               See also "isfinite", and "fpclassify".

       "isprint"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:print:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "ispunct"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:punct:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "issignaling"
                       use POSIX ':nan_payload';
                       issignaling($var, $payload)

               Return true if the argument is a signaling NaN.

               Note the API instability warning in "setpayload".

               See "nan" for more discussion about "NaN".

       "isspace"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:space:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "isupper"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:upper:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "isxdigit"
               This function has been removed as of v5.24.  It was very similar to matching
               against "qr/ ^ [[:xdigit:]]+ $ /x", which you should convert to use instead.  See
               "POSIX Character Classes" in perlrecharclass.

       "j0"
       "j1"
       "jn"
       "y0"
       "y1"
       "yn"    The Bessel function of the first kind of the order zero.

       "kill"  This is identical to Perl's builtin "kill()" function for sending signals to
               processes (often to terminate them), see "kill" in perlfunc.

       "labs"  Not implemented.  (For returning absolute values of long integers.)  "labs()" is
               C-specific, see "abs" in perlfunc instead.

       "lchown"
               This is identical to the C function, except the order of arguments is consistent
               with Perl's builtin "chown()" with the added restriction of only one path, not a
               list of paths.  Does the same thing as the "chown()" function but changes the
               owner of a symbolic link instead of the file the symbolic link points to.

                POSIX::lchown($uid, $gid, $file_path);

       "ldexp" This is identical to the C function "ldexp()" for multiplying floating point
               numbers with powers of two.

                       $x_quadrupled = POSIX::ldexp($x, 2);

       "ldiv"  Not implemented.  (For computing dividends of long integers.)  "ldiv()" is
               C-specific, use "/" and "int()" instead.

       "lgamma"
               The logarithm of the Gamma function [C99].

               See also "tgamma".

       "log1p" Equivalent to "log(1 + x)", but more stable results for small argument values
               [C99].

       "log2"  Logarithm base two [C99].

               See also "expm1".

       "logb"  Integer binary logarithm [C99].

               For example "logb(20)" is 4, as a floating point number.

               See also "ilogb".

       "link"  This is identical to Perl's builtin "link()" function for creating hard links into
               files, see "link" in perlfunc.

       "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 perllocale, which provides a comprehensive discussion of Perl locale
               handling, including a section devoted to this 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 interefere with a thread that has called "switch_to_global_locale" in perlapi.

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

                       my $loc = POSIX::setlocale( &POSIX::LC_ALL, "de" );
                       print "Locale: \"$loc\"\n";
                       my $lconv = POSIX::localeconv();
                       foreach my $property (qw(
                               decimal_point
                               thousands_sep
                               grouping
                               int_curr_symbol
                               currency_symbol
                               mon_decimal_point
                               mon_thousands_sep
                               mon_grouping
                               positive_sign
                               negative_sign
                               int_frac_digits
                               frac_digits
                               p_cs_precedes
                               p_sep_by_space
                               n_cs_precedes
                               n_sep_by_space
                               p_sign_posn
                               n_sign_posn
                               int_p_cs_precedes
                               int_p_sep_by_space
                               int_n_cs_precedes
                               int_n_sep_by_space
                               int_p_sign_posn
                               int_n_sign_posn
                       ))
                       {
                               printf qq(%s: "%s",\n),
                                       $property, $lconv->{$property};
                       }

               The members whose names begin with "int_p_" and "int_n_" were added by
               POSIX.1-2008 and are only available on systems that support them.

       "localtime"
               This is identical to Perl's builtin "localtime()" function for converting seconds
               since the epoch to a date see "localtime" in perlfunc except that
               "POSIX::localtime()" must be provided an explicit value (rather than relying on an
               implicit $_):

                   @localtime = POSIX::localtime(time);    # good

                   @localtime = localtime();               # good

                   @localtime = POSIX::localtime();        # throws exception

       "log"   This is identical to Perl's builtin "log()" function, returning the natural
               (e-based) logarithm of the numerical argument, see "log" in perlfunc.

       "log10" This is identical to the C function "log10()", returning the 10-base logarithm of
               the numerical argument.  You can also use

                   sub log10 { log($_[0]) / log(10) }

               or

                   sub log10 { log($_[0]) / 2.30258509299405 }

               or

                   sub log10 { log($_[0]) * 0.434294481903252 }

       "longjmp"
               Not implemented.  "longjmp()" is C-specific: use "die" in perlfunc instead.

       "lseek" Move the file's read/write position.  This uses file descriptors such as those
               obtained by calling "POSIX::open".

                       $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
                       $off_t = POSIX::lseek( $fd, 0, &POSIX::SEEK_SET );

               Returns "undef" on failure.

       "lrint" Depending on the current floating point rounding mode, rounds the argument either
               toward nearest (like "round"), toward zero (like "trunc"), downward (toward
               negative infinity), or upward (toward positive infinity) [C99].

               For the rounding mode, see "fegetround".

       "lround"
               Like "round", but as integer, as opposed to floating point [C99].

               See also "ceil", "floor", "trunc".

               Owing to an oversight, this is not currently exported by default, or as part of
               the ":math_h_c99" export tag; importing it must therefore be done by explicit
               name.

       "malloc"
               Not implemented.  "malloc()" is C-specific.  Perl does memory management
               transparently.

       "mblen" This is identical to the C function "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 perluniintro.

       "mbstowcs"
               This is identical to the C function "mbstowcs()".

               See "mblen".

       "mbtowc"
               This is identical to the C function "mbtowc()".

               See "mblen".

       "memchr"
               Not implemented.  "memchr()" is C-specific, see "index" in perlfunc instead.

       "memcmp"
               Not implemented.  "memcmp()" is C-specific, use "eq" instead, see perlop.

       "memcpy"
               Not implemented.  "memcpy()" is C-specific, use "=", see perlop, or see "substr"
               in perlfunc.

       "memmove"
               Not implemented.  "memmove()" is C-specific, use "=", see perlop, or see "substr"
               in perlfunc.

       "memset"
               Not implemented.  "memset()" is C-specific, use "x" instead, see perlop.

       "mkdir" This is identical to Perl's builtin "mkdir()" function for creating directories,
               see "mkdir" in perlfunc.

       "mkfifo"
               This is similar to the C function "mkfifo()" for creating FIFO special files.

                       if (mkfifo($path, $mode)) { ....

               Returns "undef" on failure.  The $mode is similar to the mode of "mkdir()", see
               "mkdir" in perlfunc, though for "mkfifo" you must specify the $mode.

       "mktime"
               Convert date/time info to a calendar time.

               Synopsis:

                       mktime(sec, min, hour, mday, mon, year, wday = 0,
                              yday = 0, isdst = -1)

               The month ("mon"), weekday ("wday"), and yearday ("yday") begin at zero, i.e.,
               January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1.  The year
               ("year") is given in years since 1900; i.e., the year 1995 is 95; the year 2001 is
               101.  Consult your system's "mktime()" manpage for details about these and the
               other arguments.

               Calendar time for December 12, 1995, at 10:30 am.

                       $time_t = POSIX::mktime( 0, 30, 10, 12, 11, 95 );
                       print "Date = ", POSIX::ctime($time_t);

               Returns "undef" on failure.

       "modf"  Return the integral and fractional parts of a floating-point number.

                       ($fractional, $integral) = POSIX::modf( 3.14 );

               See also "round".

       "NaN"   The not-a-number as a constant:

                  use POSIX qw(NaN);
                  my $nan = NaN;

               See also "nan", "/isnan", and "fpclassify".

       "nan"
                  my $nan = nan();

               Returns "NaN", not-a-number [C99].

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

               With an argument, can be used to generate a NaN with payload.  The argument is
               first interpreted as a floating point number, but then any fractional parts are
               truncated (towards zero), and the value is interpreted as an unsigned integer.
               The bits of this integer are stored in the unused bits of the NaN.

               The result has a dual nature: it is a NaN, but it also carries the integer inside
               it.  The integer can be retrieved with "getpayload".  Note, though, that the
               payload is not propagated, not even on copies, and definitely not in arithmetic
               operations.

               How many bits fit in the NaN depends on what kind of floating points are being
               used, but on the most common platforms (64-bit IEEE 754, or the x86 80-bit long
               doubles) there are 51 and 61 bits available, respectively.  (There would be 52 and
               62, but the quiet/signaling bit of NaNs takes away one.)  However, because of the
               floating-point-to- integer-and-back conversions, please test carefully whether you
               get back what you put in.  If your integers are only 32 bits wide, you probably
               should not rely on more than 32 bits of payload.

               Whether a "signaling" NaN is in any way different from a "quiet" NaN, depends on
               the platform.  Also note that the payload of the default NaN (no argument to
               nan()) is not necessarily zero, use "setpayload" to explicitly set the payload.
               On some platforms like the 32-bit x86, (unless using the 80-bit long doubles) the
               signaling bit is not supported at all.

               See also "isnan", "NaN", "setpayload" and "issignaling".

       "nearbyint"
               Returns the nearest integer to the argument, according to the current rounding
               mode (see "fegetround") [C99].

       "nextafter"
               Returns the next representable floating point number after "x" in the direction of
               "y" [C99].

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

               Like "nexttoward", but potentially less accurate.

       "nexttoward"
               Returns the next representable floating point number after "x" in the direction of
               "y" [C99].

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

               Like "nextafter", but potentially more accurate.

       "nice"  This is similar to the C function "nice()", for changing the scheduling preference
               of the current process.  Positive arguments mean a more polite process, negative
               values a more needy process.  Normal (non-root) user processes can only change
               towards being more polite.

               Returns "undef" on failure.

       "offsetof"
               Not implemented.  "offsetof()" is C-specific, you probably want to see "pack" in
               perlfunc instead.

       "open"  Open a file for reading for writing.  This returns file descriptors, not Perl
               filehandles.  Use "POSIX::close" to close the file.

               Open a file read-only with mode 0666.

                       $fd = POSIX::open( "foo" );

               Open a file for read and write.

                       $fd = POSIX::open( "foo", &POSIX::O_RDWR );

               Open a file for write, with truncation.

                       $fd = POSIX::open(
                               "foo", &POSIX::O_WRONLY | &POSIX::O_TRUNC
                       );

               Create a new file with mode 0640.  Set up the file for writing.

                       $fd = POSIX::open(
                               "foo", &POSIX::O_CREAT | &POSIX::O_WRONLY, 0640
                       );

               Returns "undef" on failure.

               See also "sysopen" in perlfunc.

       "opendir"
               Open a directory for reading.

                       $dir = POSIX::opendir( "/var" );
                       @files = POSIX::readdir( $dir );
                       POSIX::closedir( $dir );

               Returns "undef" on failure.

       "pathconf"
               Retrieves the value of a configurable limit on a file or directory.

               The following will determine the maximum length of the longest allowable pathname
               on the filesystem which holds "/var".

                       $path_max = POSIX::pathconf( "/var",
                                                     &POSIX::_PC_PATH_MAX );

               Returns "undef" on failure.

       "pause" This is similar to the C function "pause()", which suspends the execution of the
               current process until a signal is received.

               Returns "undef" on failure.

       "perror"
               This is identical to the C function "perror()", which outputs to the standard
               error stream the specified message followed by ": " and the current error string.
               Use the "warn()" function and the $!  variable instead, see "warn" in perlfunc and
               "$ERRNO" in perlvar.

       "pipe"  Create an interprocess channel.  This returns file descriptors like those returned
               by "POSIX::open".

                       my ($read, $write) = POSIX::pipe();
                       POSIX::write( $write, "hello", 5 );
                       POSIX::read( $read, $buf, 5 );

               See also "pipe" in perlfunc.

       "pow"   Computes $x raised to the power $exponent.

                       $ret = POSIX::pow( $x, $exponent );

               You can also use the "**" operator, see perlop.

       "printf"
               Formats and prints the specified arguments to "STDOUT".  See also "printf" in
               perlfunc.

       "putc"  Not implemented.  "putc()" is C-specific, see "print" in perlfunc instead.

       "putchar"
               Not implemented.  "putchar()" is C-specific, see "print" in perlfunc instead.

       "puts"  Not implemented.  "puts()" is C-specific, see "print" in perlfunc instead.

       "qsort" Not implemented.  "qsort()" is C-specific, see "sort" in perlfunc instead.

       "raise" Sends the specified signal to the current process.  See also "kill" in perlfunc
               and the $$ in "$PID" in perlvar.

       "rand"  Not implemented.  "rand()" is non-portable, see "rand" in perlfunc instead.

       "read"  Read from a file.  This uses file descriptors such as those obtained by calling
               "POSIX::open".  If the buffer $buf is not large enough for the read then Perl will
               extend it to make room for the request.

                       $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
                       $bytes = POSIX::read( $fd, $buf, 3 );

               Returns "undef" on failure.

               See also "sysread" in perlfunc.

       "readdir"
               This is identical to Perl's builtin "readdir()" function for reading directory
               entries, see "readdir" in perlfunc.

       "realloc"
               Not implemented.  "realloc()" is C-specific.  Perl does memory management
               transparently.

       "remainder"
               Given "x" and "y", returns the value "x - n*y", where "n" is the integer closest
               to "x"/"y". [C99]

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

               See also "remquo".

       "remove"
               Deletes a name from the filesystem.  Calls "unlink" in perlfunc for files and
               "rmdir" in perlfunc for directories.

       "remquo"
               Like "remainder" but also returns the low-order bits of the quotient (n) [C99]

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

       "rename"
               This is identical to Perl's builtin "rename()" function for renaming files, see
               "rename" in perlfunc.

       "rewind"
               Seeks to the beginning of the file.

       "rewinddir"
               This is identical to Perl's builtin "rewinddir()" function for rewinding directory
               entry streams, see "rewinddir" in perlfunc.

       "rint"  Identical to "lrint".

       "rmdir" This is identical to Perl's builtin "rmdir()" function for removing (empty)
               directories, see "rmdir" in perlfunc.

       "round" Returns the integer (but still as floating point) nearest to the argument [C99].

               See also "ceil", "floor", "lround", "modf", and "trunc".

       "scalbn"
               Returns "x * 2**y" [C99].

               See also "frexp" and "ldexp".

       "scanf" Not implemented.  "scanf()" is C-specific, use <> and regular expressions instead,
               see perlre.

       "setgid"
               Sets the real group identifier and the effective group identifier for this
               process.  Similar to assigning a value to the Perl's builtin $) variable, see
               "$EGID" in perlvar, except that the latter will change only the real user
               identifier, and that the setgid() uses only a single numeric argument, as opposed
               to a space-separated list of numbers.

       "setjmp"
               Not implemented.  "setjmp()" is C-specific: use "eval {}" instead, see "eval" in
               perlfunc.

       "setlocale"
               WARNING!  Do NOT use this function in a thread.  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 function
               should read perllocale, whch provides a comprehensive discussion of Perl locale
               handling, knowledge of which is necessary to properly use this function.  It
               contains a section devoted to this function.  The discussion here is merely a
               summary reference for "setlocale()".  Note that Perl itself is almost entirely
               unaffected by the locale except within the scope of "use locale".  (Exceptions are
               listed in "Not within the scope of "use locale"" in perllocale.)

               The following examples assume

                       use POSIX qw(setlocale LC_ALL LC_CTYPE);

               has been issued.

               The following will set the traditional UNIX system locale behavior (the second
               argument "C").

                       $loc = setlocale( LC_ALL, "C" );

               The following will query the current "LC_CTYPE" category.  (No second argument
               means 'query'.)

                       $loc = setlocale( LC_CTYPE );

               The following will set the "LC_CTYPE" behaviour according to the locale
               environment variables (the second argument "").  Please see your system's
               setlocale(3) documentation for the locale environment variables' meaning or
               consult perllocale.

                       $loc = setlocale( LC_CTYPE, "" );

               The following will set the "LC_COLLATE" behaviour to Argentinian Spanish. NOTE:
               The naming and availability of locales depends on your operating system. Please
               consult perllocale for how to find out which locales are available in your system.

                       $loc = setlocale( LC_COLLATE, "es_AR.ISO8859-1" );

       "setpayload"
                       use POSIX ':nan_payload';
                       setpayload($var, $payload);

               Sets the "NaN" payload of var.

               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 may change.

               See "nan" for more discussion about "NaN".

               See also "setpayloadsig", "isnan", "getpayload", and "issignaling".

       "setpayloadsig"
                       use POSIX ':nan_payload';
                       setpayloadsig($var, $payload);

               Like "setpayload" but also makes the NaN signaling.

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

               Note the API instability warning in "setpayload".

               Note that because how the floating point formats work out, on the most common
               platforms signaling payload of zero is best avoided, since it might end up being
               identical to "+Inf".

               See also "nan", "isnan", "getpayload", and "issignaling".

       "setpgid"
               This is similar to the C function "setpgid()" for setting the process group
               identifier of the current process.

               Returns "undef" on failure.

       "setsid"
               This is identical to the C function "setsid()" for setting the session identifier
               of the current process.

       "setuid"
               Sets the real user identifier and the effective user identifier for this process.
               Similar to assigning a value to the Perl's builtin $< variable, see "$UID" in
               perlvar, except that the latter will change only the real user identifier.

       "sigaction"
               Detailed signal management.  This uses "POSIX::SigAction" objects for the "action"
               and "oldaction" arguments (the oldaction can also be just a hash reference).
               Consult your system's "sigaction" manpage for details, see also "POSIX::SigRt".

               Synopsis:

                       sigaction(signal, action, oldaction = 0)

               Returns "undef" on failure.  The "signal" must be a number (like "SIGHUP"), not a
               string (like "SIGHUP"), though Perl does try hard to understand you.

               If you use the "SA_SIGINFO" flag, the signal handler will in addition to the first
               argument, the signal name, also receive a second argument, a hash reference,
               inside which are the following keys with the following semantics, as defined by
               POSIX/SUSv3:

                   signo       the signal number
                   errno       the error number
                   code        if this is zero or less, the signal was sent by
                               a user process and the uid and pid make sense,
                               otherwise the signal was sent by the kernel

               The constants for specific "code" values can be imported individually or using the
               ":signal_h_si_code" tag.

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

                   pid         the process id generating the signal
                   uid         the uid of the process id generating the signal
                   status      exit value or signal for SIGCHLD
                   band        band event for SIGPOLL
                   addr        address of faulting instruction or memory
                               reference for SIGILL, SIGFPE, SIGSEGV or SIGBUS

               A third argument is also passed to the handler, which contains a copy of the raw
               binary contents of the "siginfo" structure: if a system has some non-POSIX fields,
               this third argument is where to "unpack()" them from.

               Note that not all "siginfo" values make sense simultaneously (some are valid only
               for certain signals, for example), and not all values make sense from Perl
               perspective, you should to consult your system's "sigaction" and possibly also
               "siginfo" documentation.

       "siglongjmp"
               Not implemented.  "siglongjmp()" is C-specific: use "die" in perlfunc instead.

       "signbit"
               Returns zero for positive arguments, non-zero for negative arguments [C99].

       "sigpending"
               Examine signals that are blocked and pending.  This uses "POSIX::SigSet" objects
               for the "sigset" argument.  Consult your system's "sigpending" manpage for
               details.

               Synopsis:

                       sigpending(sigset)

               Returns "undef" on failure.

       "sigprocmask"
               Change and/or examine calling process's signal mask.  This uses "POSIX::SigSet"
               objects for the "sigset" and "oldsigset" arguments.  Consult your system's
               "sigprocmask" manpage for details.

               Synopsis:

                       sigprocmask(how, sigset, oldsigset = 0)

               Returns "undef" on failure.

               Note that you can't reliably block or unblock a signal from its own signal handler
               if you're using safe signals. Other signals can be blocked or unblocked reliably.

       "sigsetjmp"
               Not implemented.  "sigsetjmp()" is C-specific: use "eval {}" instead, see "eval"
               in perlfunc.

       "sigsuspend"
               Install a signal mask and suspend process until signal arrives.  This uses
               "POSIX::SigSet" objects for the "signal_mask" argument.  Consult your system's
               "sigsuspend" manpage for details.

               Synopsis:

                       sigsuspend(signal_mask)

               Returns "undef" on failure.

       "sin"   This is identical to Perl's builtin "sin()" function for returning the sine of the
               numerical argument, see "sin" in perlfunc.  See also Math::Trig.

       "sinh"  This is identical to the C function "sinh()" for returning the hyperbolic sine of
               the numerical argument.  See also Math::Trig.

       "sleep" This is functionally identical to Perl's builtin "sleep()" function for suspending
               the execution of the current for process for certain number of seconds, see
               "sleep" in perlfunc.  There is one significant difference, however:
               "POSIX::sleep()" returns the number of unslept seconds, while the "CORE::sleep()"
               returns the number of slept seconds.

       "sprintf"
               This is similar to Perl's builtin "sprintf()" function for returning a string that
               has the arguments formatted as requested, see "sprintf" in perlfunc.

       "sqrt"  This is identical to Perl's builtin "sqrt()" function.  for returning the square
               root of the numerical argument, see "sqrt" in perlfunc.

       "srand" Give a seed the pseudorandom number generator, see "srand" in perlfunc.

       "sscanf"
               Not implemented.  "sscanf()" is C-specific, use regular expressions instead, see
               perlre.

       "stat"  This is identical to Perl's builtin "stat()" function for returning information
               about files and directories.

       "strcat"
               Not implemented.  "strcat()" is C-specific, use ".=" instead, see perlop.

       "strchr"
               Not implemented.  "strchr()" is C-specific, see "index" in perlfunc instead.

       "strcmp"
               Not implemented.  "strcmp()" is C-specific, use "eq" or "cmp" instead, see perlop.

       "strcoll"
               This is identical to the C function "strcoll()" for collating (comparing) strings
               transformed using the "strxfrm()" function.  Not really needed since Perl can do
               this transparently, see perllocale.

               Beware that in a UTF-8 locale, anything you pass to this function must be in
               UTF-8; and when not in a UTF-8 locale, anything passed must not be UTF-8 encoded.

       "strcpy"
               Not implemented.  "strcpy()" is C-specific, use "=" instead, see perlop.

       "strcspn"
               Not implemented.  "strcspn()" is C-specific, use regular expressions instead, see
               perlre.

       "strerror"
               Returns the error string for the specified errno.  Identical to the string form of
               $!, see "$ERRNO" in perlvar.

       "strftime"
               Convert date and time information to string.  Returns the string.

               Synopsis:

                       strftime(fmt, sec, min, hour, mday, mon, year,
                                wday = -1, yday = -1, isdst = -1)

               The month ("mon"), weekday ("wday"), and yearday ("yday") begin at zero, i.e.,
               January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1.  The year
               ("year") is given in years since 1900, i.e., the year 1995 is 95; the year 2001 is
               101.  Consult your system's "strftime()" manpage for details about these and the
               other arguments.

               If you want your code to be portable, your format ("fmt") argument should use only
               the conversion specifiers defined by the ANSI C standard (C89, to play safe).
               These are "aAbBcdHIjmMpSUwWxXyYZ%".  But even then, the results of some of the
               conversion specifiers are non-portable.  For example, the specifiers "aAbBcpZ"
               change according to the locale settings of the user, and both how to set locales
               (the locale names) and what output to expect are non-standard.  The specifier "c"
               changes according to the timezone settings of the user and the timezone
               computation rules of the operating system.  The "Z" specifier is notoriously
               unportable since the names of timezones are non-standard. Sticking to the numeric
               specifiers is the safest route.

               The given arguments are made consistent as though by calling "mktime()" before
               calling your system's "strftime()" function, except that the "isdst" value is not
               affected.

               The string for Tuesday, December 12, 1995.

                       $str = POSIX::strftime( "%A, %B %d, %Y",
                                                0, 0, 0, 12, 11, 95, 2 );
                       print "$str\n";

       "strlen"
               Not implemented.  "strlen()" is C-specific, use "length()" instead, see "length"
               in perlfunc.

       "strncat"
               Not implemented.  "strncat()" is C-specific, use ".=" instead, see perlop.

       "strncmp"
               Not implemented.  "strncmp()" is C-specific, use "eq" instead, see perlop.

       "strncpy"
               Not implemented.  "strncpy()" is C-specific, use "=" instead, see perlop.

       "strpbrk"
               Not implemented.  "strpbrk()" is C-specific, use regular expressions instead, see
               perlre.

       "strrchr"
               Not implemented.  "strrchr()" is C-specific, see "rindex" in perlfunc instead.

       "strspn"
               Not implemented.  "strspn()" is C-specific, use regular expressions instead, see
               perlre.

       "strstr"
               This is identical to Perl's builtin "index()" function, see "index" in perlfunc.

       "strtod"
               String to double translation. Returns the parsed number and the number of
               characters in the unparsed portion of the string.  Truly POSIX-compliant systems
               set $! ($ERRNO) to indicate a translation error, so clear $! before calling
               "strtod".  However, non-POSIX systems may not check for overflow, and therefore
               will never set $!.

               "strtod" respects any POSIX "setlocale()" "LC_TIME" settings, regardless of
               whether or not it is called from Perl code that is within the scope of
               "use locale".  This means 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 $str as a floating point number use

                   $! = 0;
                   ($num, $n_unparsed) = POSIX::strtod($str);

               The second returned item and $! can be used to check for valid input:

                   if (($str eq '') || ($n_unparsed != 0) || $!) {
                       die "Non-numeric input $str" . ($! ? ": $!\n" : "\n");
                   }

               When called in a scalar context "strtod" returns the parsed number.

       "strtok"
               Not implemented.  "strtok()" is C-specific, use regular expressions instead, see
               perlre, or "split" in perlfunc.

       "strtol"
               String to (long) integer translation.  Returns the parsed number and the number of
               characters in the unparsed portion of the string.  Truly POSIX-compliant systems
               set $! ($ERRNO) to indicate a translation error, so clear $! before calling
               "strtol".  However, non-POSIX systems may not check for overflow, and therefore
               will never set $!.

               "strtol" should respect any POSIX setlocale() settings.

               To parse a string $str as a number in some base $base use

                   $! = 0;
                   ($num, $n_unparsed) = POSIX::strtol($str, $base);

               The base should be zero or between 2 and 36, inclusive.  When the base is zero or
               omitted "strtol" will use the string itself to determine the base: a leading "0x"
               or "0X" means hexadecimal; a leading "0" means octal; any other leading characters
               mean decimal.  Thus, "1234" is parsed as a decimal number, "01234" as an octal
               number, and "0x1234" as a hexadecimal number.

               The second returned item and $! can be used to check for valid input:

                   if (($str eq '') || ($n_unparsed != 0) || !$!) {
                       die "Non-numeric input $str" . $! ? ": $!\n" : "\n";
                   }

               When called in a scalar context "strtol" returns the parsed number.

       "strtold"
               Like "strtod" but for long doubles.  Defined only if the system supports long
               doubles.

       "strtoul"
               String to unsigned (long) integer translation.  "strtoul()" is identical to
               "strtol()" except that "strtoul()" only parses unsigned integers.  See "strtol"
               for details.

               Note: Some vendors supply "strtod()" and "strtol()" but not "strtoul()".  Other
               vendors that do supply "strtoul()" parse "-1" as a valid value.

       "strxfrm"
               String transformation.  Returns the transformed string.

                       $dst = POSIX::strxfrm( $src );

               Used in conjunction with the "strcoll()" function, see "strcoll".

               Not really needed since Perl can do this transparently, see perllocale.

               Beware that in a UTF-8 locale, anything you pass to this function must be in
               UTF-8; and when not in a UTF-8 locale, anything passed must not be UTF-8 encoded.

       "sysconf"
               Retrieves values of system configurable variables.

               The following will get the machine's clock speed.

                       $clock_ticks = POSIX::sysconf( &POSIX::_SC_CLK_TCK );

               Returns "undef" on failure.

       "system"
               This is identical to Perl's builtin "system()" function, see "system" in perlfunc.

       "tan"   This is identical to the C function "tan()", returning the tangent of the
               numerical argument.  See also Math::Trig.

       "tanh"  This is identical to the C function "tanh()", returning the hyperbolic tangent of
               the numerical argument.   See also Math::Trig.

       "tcdrain"
               This is similar to the C function "tcdrain()" for draining the output queue of its
               argument stream.

               Returns "undef" on failure.

       "tcflow"
               This is similar to the C function "tcflow()" for controlling the flow of its
               argument stream.

               Returns "undef" on failure.

       "tcflush"
               This is similar to the C function "tcflush()" for flushing the I/O buffers of its
               argument stream.

               Returns "undef" on failure.

       "tcgetpgrp"
               This is identical to the C function "tcgetpgrp()" for returning the process group
               identifier of the foreground process group of the controlling terminal.

       "tcsendbreak"
               This is similar to the C function "tcsendbreak()" for sending a break on its
               argument stream.

               Returns "undef" on failure.

       "tcsetpgrp"
               This is similar to the C function "tcsetpgrp()" for setting the process group
               identifier of the foreground process group of the controlling terminal.

               Returns "undef" on failure.

       "tgamma"
               The Gamma function [C99].

               See also "lgamma".

       "time"  This is identical to Perl's builtin "time()" function for returning the number of
               seconds since the epoch (whatever it is for the system), see "time" in perlfunc.

       "times" The "times()" function returns elapsed realtime since some point in the past (such
               as system startup), user and system times for this process, and user and system
               times used by child processes.  All times are returned in clock ticks.

                   ($realtime, $user, $system, $cuser, $csystem)
                       = POSIX::times();

               Note: Perl's builtin "times()" function returns four values, measured in seconds.

       "tmpfile"
               Not implemented.  Use method "IO::File::new_tmpfile()" instead, or see File::Temp.

       "tmpnam"
               For security reasons, which are probably detailed in your system's documentation
               for the C library "tmpnam()" function, this interface is no longer available;
               instead use File::Temp.

       "tolower"
               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 "lc()" function, see "lc" in perlfunc, see "lc" in
               perlfunc, or the equivalent "\L" operator inside doublequotish strings.

       "toupper"
               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 "uc()" function, see "uc" in perlfunc, or the equivalent "\U"
               operator inside doublequotish strings.

       "trunc" Returns the integer toward zero from the argument [C99].

               See also "ceil", "floor", and "round".

       "ttyname"
               This is identical to the C function "ttyname()" for returning the name of the
               current terminal.

       "tzname"
               Retrieves the time conversion information from the "tzname" variable.

                       POSIX::tzset();
                       ($std, $dst) = POSIX::tzname();

       "tzset" This is identical to the C function "tzset()" for setting the current timezone
               based on the environment variable "TZ", to be used by "ctime()", "localtime()",
               "mktime()", and "strftime()" functions.

       "umask" This is identical to Perl's builtin "umask()" function for setting (and querying)
               the file creation permission mask, see "umask" in perlfunc.

       "uname" Get name of current operating system.

                       ($sysname, $nodename, $release, $version, $machine)
                               = POSIX::uname();

               Note that the actual meanings of the various fields are not that well
               standardized, do not expect any great portability.  The $sysname might be the name
               of the operating system, the $nodename might be the name of the host, the $release
               might be the (major) release number of the operating system, the $version might be
               the (minor) release number of the operating system, and the $machine might be a
               hardware identifier.  Maybe.

       "ungetc"
               Not implemented.  Use method "IO::Handle::ungetc()" instead.

       "unlink"
               This is identical to Perl's builtin "unlink()" function for removing files, see
               "unlink" in perlfunc.

       "utime" This is identical to Perl's builtin "utime()" function for changing the time
               stamps of files and directories, see "utime" in perlfunc.

       "vfprintf"
               Not implemented.  "vfprintf()" is C-specific, see "printf" in perlfunc instead.

       "vprintf"
               Not implemented.  "vprintf()" is C-specific, see "printf" in perlfunc instead.

       "vsprintf"
               Not implemented.  "vsprintf()" is C-specific, see "sprintf" in perlfunc instead.

       "wait"  This is identical to Perl's builtin "wait()" function, see "wait" in perlfunc.

       "waitpid"
               Wait for a child process to change state.  This is identical to Perl's builtin
               "waitpid()" function, see "waitpid" in perlfunc.

                       $pid = POSIX::waitpid( -1, POSIX::WNOHANG );
                       print "status = ", ($? / 256), "\n";

       "wcstombs"
               This is identical to the C function "wcstombs()".

               See "mblen".

       "wctomb"
               This is identical to the C function "wctomb()".

               See "mblen".

       "write" Write to a file.  This uses file descriptors such as those obtained by calling
               "POSIX::open".

                       $fd = POSIX::open( "foo", &POSIX::O_WRONLY );
                       $buf = "hello";
                       $bytes = POSIX::write( $fd, $buf, 5 );

               Returns "undef" on failure.

               See also "syswrite" in perlfunc.

CLASSES

   "POSIX::SigAction"
       "new"   Creates a new "POSIX::SigAction" object which corresponds to the C "struct
               sigaction".  This object will be destroyed automatically when it is no longer
               needed.  The first parameter is the handler, a sub reference.  The second
               parameter is a "POSIX::SigSet" object, it defaults to the empty set.  The third
               parameter contains the "sa_flags", it defaults to 0.

                       $sigset = POSIX::SigSet->new(SIGINT, SIGQUIT);
                       $sigaction = POSIX::SigAction->new(
                                       \&handler, $sigset, &POSIX::SA_NOCLDSTOP
                                    );

               This "POSIX::SigAction" object is intended for use with the "POSIX::sigaction()"
               function.

       "handler"
       "mask"
       "flags" accessor functions to get/set the values of a SigAction object.

                       $sigset = $sigaction->mask;
                       $sigaction->flags(&POSIX::SA_RESTART);

       "safe"  accessor function for the "safe signals" flag of a SigAction object; see perlipc
               for general information on safe (a.k.a. "deferred") signals.  If you wish to
               handle a signal safely, use this accessor to set the "safe" flag in the
               "POSIX::SigAction" object:

                       $sigaction->safe(1);

               You may also examine the "safe" flag on the output action object which is filled
               in when given as the third parameter to "POSIX::sigaction()":

                       sigaction(SIGINT, $new_action, $old_action);
                       if ($old_action->safe) {
                           # previous SIGINT handler used safe signals
                       }

   "POSIX::SigRt"
       %SIGRT  A hash of the POSIX realtime signal handlers.  It is an extension of the standard
               %SIG, the $POSIX::SIGRT{SIGRTMIN} is roughly equivalent to $SIG{SIGRTMIN}, but the
               right POSIX moves (see below) are made with the "POSIX::SigSet" and
               "POSIX::sigaction" instead of accessing the %SIG.

               You can set the %POSIX::SIGRT elements to set the POSIX realtime signal handlers,
               use "delete" and "exists" on the elements, and use "scalar" on the %POSIX::SIGRT
               to find out how many POSIX realtime signals there are available
               "(SIGRTMAX - SIGRTMIN + 1", the "SIGRTMAX" is a valid POSIX realtime signal).

               Setting the %SIGRT elements is equivalent to calling this:

                 sub new {
                   my ($rtsig, $handler, $flags) = @_;
                   my $sigset = POSIX::SigSet($rtsig);
                   my $sigact = POSIX::SigAction->new($handler,$sigset,$flags);
                   sigaction($rtsig, $sigact);
                 }

               The flags default to zero, if you want something different you can either use
               "local" on $POSIX::SigRt::SIGACTION_FLAGS, or you can derive from POSIX::SigRt and
               define your own "new()" (the tied hash STORE method of the %SIGRT calls
               "new($rtsig, $handler, $SIGACTION_FLAGS)", where the $rtsig ranges from zero to
               "SIGRTMAX - SIGRTMIN + 1)".

               Just as with any signal, you can use "sigaction($rtsig, undef, $oa)" to retrieve
               the installed signal handler (or, rather, the signal action).

               NOTE: whether POSIX realtime signals really work in your system, or whether Perl
               has been compiled so that it works with them, is outside of this discussion.

       "SIGRTMIN"
               Return the minimum POSIX realtime signal number available, or "undef" if no POSIX
               realtime signals are available.

       "SIGRTMAX"
               Return the maximum POSIX realtime signal number available, or "undef" if no POSIX
               realtime signals are available.

   "POSIX::SigSet"
       "new"   Create a new SigSet object.  This object will be destroyed automatically when it
               is no longer needed.  Arguments may be supplied to initialize the set.

               Create an empty set.

                       $sigset = POSIX::SigSet->new;

               Create a set with "SIGUSR1".

                       $sigset = POSIX::SigSet->new( &POSIX::SIGUSR1 );

       "addset"
               Add a signal to a SigSet object.

                       $sigset->addset( &POSIX::SIGUSR2 );

               Returns "undef" on failure.

       "delset"
               Remove a signal from the SigSet object.

                       $sigset->delset( &POSIX::SIGUSR2 );

               Returns "undef" on failure.

       "emptyset"
               Initialize the SigSet object to be empty.

                       $sigset->emptyset();

               Returns "undef" on failure.

       "fillset"
               Initialize the SigSet object to include all signals.

                       $sigset->fillset();

               Returns "undef" on failure.

       "ismember"
               Tests the SigSet object to see if it contains a specific signal.

                       if( $sigset->ismember( &POSIX::SIGUSR1 ) ){
                               print "contains SIGUSR1\n";
                       }

   "POSIX::Termios"
       "new"   Create a new Termios object.  This object will be destroyed automatically when it
               is no longer needed.  A Termios object corresponds to the "termios" C struct.
               "new()" mallocs a new one, "getattr()" fills it from a file descriptor, and
               "setattr()" sets a file descriptor's parameters to match Termios' contents.

                       $termios = POSIX::Termios->new;

       "getattr"
               Get terminal control attributes.

               Obtain the attributes for "stdin".

                       $termios->getattr( 0 ) # Recommended for clarity.
                       $termios->getattr()

               Obtain the attributes for stdout.

                       $termios->getattr( 1 )

               Returns "undef" on failure.

       "getcc" Retrieve a value from the "c_cc" field of a "termios" object.  The "c_cc" field is
               an array so an index must be specified.

                       $c_cc[1] = $termios->getcc(1);

       "getcflag"
               Retrieve the "c_cflag" field of a "termios" object.

                       $c_cflag = $termios->getcflag;

       "getiflag"
               Retrieve the "c_iflag" field of a "termios" object.

                       $c_iflag = $termios->getiflag;

       "getispeed"
               Retrieve the input baud rate.

                       $ispeed = $termios->getispeed;

       "getlflag"
               Retrieve the "c_lflag" field of a "termios" object.

                       $c_lflag = $termios->getlflag;

       "getoflag"
               Retrieve the "c_oflag" field of a "termios" object.

                       $c_oflag = $termios->getoflag;

       "getospeed"
               Retrieve the output baud rate.

                       $ospeed = $termios->getospeed;

       "setattr"
               Set terminal control attributes.

               Set attributes immediately for stdout.

                       $termios->setattr( 1, &POSIX::TCSANOW );

               Returns "undef" on failure.

       "setcc" Set a value in the "c_cc" field of a "termios" object.  The "c_cc" field is an
               array so an index must be specified.

                       $termios->setcc( &POSIX::VEOF, 1 );

       "setcflag"
               Set the "c_cflag" field of a "termios" object.

                       $termios->setcflag( $c_cflag | &POSIX::CLOCAL );

       "setiflag"
               Set the "c_iflag" field of a "termios" object.

                       $termios->setiflag( $c_iflag | &POSIX::BRKINT );

       "setispeed"
               Set the input baud rate.

                       $termios->setispeed( &POSIX::B9600 );

               Returns "undef" on failure.

       "setlflag"
               Set the "c_lflag" field of a "termios" object.

                       $termios->setlflag( $c_lflag | &POSIX::ECHO );

       "setoflag"
               Set the "c_oflag" field of a "termios" object.

                       $termios->setoflag( $c_oflag | &POSIX::OPOST );

       "setospeed"
               Set the output baud rate.

                       $termios->setospeed( &POSIX::B9600 );

               Returns "undef" on failure.

       Baud rate values
               "B38400" "B75" "B200" "B134" "B300" "B1800" "B150" "B0" "B19200" "B1200" "B9600"
               "B600" "B4800" "B50" "B2400" "B110"

       Terminal interface values
               "TCSADRAIN" "TCSANOW" "TCOON" "TCIOFLUSH" "TCOFLUSH" "TCION" "TCIFLUSH"
               "TCSAFLUSH" "TCIOFF" "TCOOFF"

       "c_cc" field values
               "VEOF" "VEOL" "VERASE" "VINTR" "VKILL" "VQUIT" "VSUSP" "VSTART" "VSTOP" "VMIN"
               "VTIME" "NCCS"

       "c_cflag" field values
               "CLOCAL" "CREAD" "CSIZE" "CS5" "CS6" "CS7" "CS8" "CSTOPB" "HUPCL" "PARENB"
               "PARODD"

       "c_iflag" field values
               "BRKINT" "ICRNL" "IGNBRK" "IGNCR" "IGNPAR" "INLCR" "INPCK" "ISTRIP" "IXOFF" "IXON"
               "PARMRK"

       "c_lflag" field values
               "ECHO" "ECHOE" "ECHOK" "ECHONL" "ICANON" "IEXTEN" "ISIG" "NOFLSH" "TOSTOP"

       "c_oflag" field values
               "OPOST"

PATHNAME CONSTANTS

       Constants
               "_PC_CHOWN_RESTRICTED" "_PC_LINK_MAX" "_PC_MAX_CANON" "_PC_MAX_INPUT"
               "_PC_NAME_MAX" "_PC_NO_TRUNC" "_PC_PATH_MAX" "_PC_PIPE_BUF" "_PC_VDISABLE"

POSIX CONSTANTS

       Constants
               "_POSIX_ARG_MAX" "_POSIX_CHILD_MAX" "_POSIX_CHOWN_RESTRICTED" "_POSIX_JOB_CONTROL"
               "_POSIX_LINK_MAX" "_POSIX_MAX_CANON" "_POSIX_MAX_INPUT" "_POSIX_NAME_MAX"
               "_POSIX_NGROUPS_MAX" "_POSIX_NO_TRUNC" "_POSIX_OPEN_MAX" "_POSIX_PATH_MAX"
               "_POSIX_PIPE_BUF" "_POSIX_SAVED_IDS" "_POSIX_SSIZE_MAX" "_POSIX_STREAM_MAX"
               "_POSIX_TZNAME_MAX" "_POSIX_VDISABLE" "_POSIX_VERSION"

RESOURCE CONSTANTS

       Imported with the ":sys_resource_h" tag.

       Constants
               "PRIO_PROCESS" "PRIO_PGRP" "PRIO_USER"

SYSTEM CONFIGURATION

       Constants
               "_SC_ARG_MAX" "_SC_CHILD_MAX" "_SC_CLK_TCK" "_SC_JOB_CONTROL" "_SC_NGROUPS_MAX"
               "_SC_OPEN_MAX" "_SC_PAGESIZE" "_SC_SAVED_IDS" "_SC_STREAM_MAX" "_SC_TZNAME_MAX"
               "_SC_VERSION"

ERRNO

       Constants
               "E2BIG" "EACCES" "EADDRINUSE" "EADDRNOTAVAIL" "EAFNOSUPPORT" "EAGAIN" "EALREADY"
               "EBADF" "EBADMSG" "EBUSY" "ECANCELED" "ECHILD" "ECONNABORTED" "ECONNREFUSED"
               "ECONNRESET" "EDEADLK" "EDESTADDRREQ" "EDOM" "EDQUOT" "EEXIST" "EFAULT" "EFBIG"
               "EHOSTDOWN" "EHOSTUNREACH" "EIDRM" "EILSEQ" "EINPROGRESS" "EINTR" "EINVAL" "EIO"
               "EISCONN" "EISDIR" "ELOOP" "EMFILE" "EMLINK" "EMSGSIZE" "ENAMETOOLONG" "ENETDOWN"
               "ENETRESET" "ENETUNREACH" "ENFILE" "ENOBUFS" "ENODATA" "ENODEV" "ENOENT" "ENOEXEC"
               "ENOLCK" "ENOLINK" "ENOMEM" "ENOMSG" "ENOPROTOOPT" "ENOSPC" "ENOSR" "ENOSTR"
               "ENOSYS" "ENOTBLK" "ENOTCONN" "ENOTDIR" "ENOTEMPTY" "ENOTRECOVERABLE" "ENOTSOCK"
               "ENOTSUP" "ENOTTY" "ENXIO" "EOPNOTSUPP" "EOTHER" "EOVERFLOW" "EOWNERDEAD" "EPERM"
               "EPFNOSUPPORT" "EPIPE" "EPROCLIM" "EPROTO" "EPROTONOSUPPORT" "EPROTOTYPE" "ERANGE"
               "EREMOTE" "ERESTART" "EROFS" "ESHUTDOWN" "ESOCKTNOSUPPORT" "ESPIPE" "ESRCH"
               "ESTALE" "ETIME" "ETIMEDOUT" "ETOOMANYREFS" "ETXTBSY" "EUSERS" "EWOULDBLOCK"
               "EXDEV"

FCNTL

       Constants
               "FD_CLOEXEC" "F_DUPFD" "F_GETFD" "F_GETFL" "F_GETLK" "F_OK" "F_RDLCK" "F_SETFD"
               "F_SETFL" "F_SETLK" "F_SETLKW" "F_UNLCK" "F_WRLCK" "O_ACCMODE" "O_APPEND"
               "O_CREAT" "O_EXCL" "O_NOCTTY" "O_NONBLOCK" "O_RDONLY" "O_RDWR" "O_TRUNC"
               "O_WRONLY"

FLOAT

       Constants
               "DBL_DIG" "DBL_EPSILON" "DBL_MANT_DIG" "DBL_MAX" "DBL_MAX_10_EXP" "DBL_MAX_EXP"
               "DBL_MIN" "DBL_MIN_10_EXP" "DBL_MIN_EXP" "FLT_DIG" "FLT_EPSILON" "FLT_MANT_DIG"
               "FLT_MAX" "FLT_MAX_10_EXP" "FLT_MAX_EXP" "FLT_MIN" "FLT_MIN_10_EXP" "FLT_MIN_EXP"
               "FLT_RADIX" "FLT_ROUNDS" "LDBL_DIG" "LDBL_EPSILON" "LDBL_MANT_DIG" "LDBL_MAX"
               "LDBL_MAX_10_EXP" "LDBL_MAX_EXP" "LDBL_MIN" "LDBL_MIN_10_EXP" "LDBL_MIN_EXP"

FLOATING-POINT ENVIRONMENT

       Constants
               "FE_DOWNWARD" "FE_TONEAREST" "FE_TOWARDZERO" "FE_UPWARD" on systems that support
               them.

LIMITS

       Constants
               "ARG_MAX" "CHAR_BIT" "CHAR_MAX" "CHAR_MIN" "CHILD_MAX" "INT_MAX" "INT_MIN"
               "LINK_MAX" "LONG_MAX" "LONG_MIN" "MAX_CANON" "MAX_INPUT" "MB_LEN_MAX" "NAME_MAX"
               "NGROUPS_MAX" "OPEN_MAX" "PATH_MAX" "PIPE_BUF" "SCHAR_MAX" "SCHAR_MIN" "SHRT_MAX"
               "SHRT_MIN" "SSIZE_MAX" "STREAM_MAX" "TZNAME_MAX" "UCHAR_MAX" "UINT_MAX"
               "ULONG_MAX" "USHRT_MAX"

LOCALE

       Constants
               "LC_ALL" "LC_COLLATE" "LC_CTYPE" "LC_MONETARY" "LC_NUMERIC" "LC_TIME"
               "LC_MESSAGES" on systems that support them.

MATH

       Constants
               "HUGE_VAL"

               "FP_ILOGB0" "FP_ILOGBNAN" "FP_INFINITE" "FP_NAN" "FP_NORMAL" "FP_SUBNORMAL"
               "FP_ZERO" "INFINITY" "NAN" "Inf" "NaN" "M_1_PI" "M_2_PI" "M_2_SQRTPI" "M_E"
               "M_LN10" "M_LN2" "M_LOG10E" "M_LOG2E" "M_PI" "M_PI_2" "M_PI_4" "M_SQRT1_2"
               "M_SQRT2" on systems with C99 support.

SIGNAL

       Constants
               "SA_NOCLDSTOP" "SA_NOCLDWAIT" "SA_NODEFER" "SA_ONSTACK" "SA_RESETHAND"
               "SA_RESTART" "SA_SIGINFO" "SIGABRT" "SIGALRM" "SIGCHLD" "SIGCONT" "SIGFPE"
               "SIGHUP" "SIGILL" "SIGINT" "SIGKILL" "SIGPIPE" "SIGQUIT" "SIGSEGV" "SIGSTOP"
               "SIGTERM" "SIGTSTP" "SIGTTIN" "SIGTTOU" "SIGUSR1" "SIGUSR2" "SIG_BLOCK" "SIG_DFL"
               "SIG_ERR" "SIG_IGN" "SIG_SETMASK" "SIG_UNBLOCK" "ILL_ILLOPC" "ILL_ILLOPN"
               "ILL_ILLADR" "ILL_ILLTRP" "ILL_PRVOPC" "ILL_PRVREG" "ILL_COPROC" "ILL_BADSTK"
               "FPE_INTDIV" "FPE_INTOVF" "FPE_FLTDIV" "FPE_FLTOVF" "FPE_FLTUND" "FPE_FLTRES"
               "FPE_FLTINV" "FPE_FLTSUB" "SEGV_MAPERR" "SEGV_ACCERR" "BUS_ADRALN" "BUS_ADRERR"
               "BUS_OBJERR" "TRAP_BRKPT" "TRAP_TRACE" "CLD_EXITED" "CLD_KILLED" "CLD_DUMPED"
               "CLD_TRAPPED" "CLD_STOPPED" "CLD_CONTINUED" "POLL_IN" "POLL_OUT" "POLL_MSG"
               "POLL_ERR" "POLL_PRI" "POLL_HUP" "SI_USER" "SI_QUEUE" "SI_TIMER" "SI_ASYNCIO"
               "SI_MESGQ"

STAT

       Constants
               "S_IRGRP" "S_IROTH" "S_IRUSR" "S_IRWXG" "S_IRWXO" "S_IRWXU" "S_ISGID" "S_ISUID"
               "S_IWGRP" "S_IWOTH" "S_IWUSR" "S_IXGRP" "S_IXOTH" "S_IXUSR"

       Macros  "S_ISBLK" "S_ISCHR" "S_ISDIR" "S_ISFIFO" "S_ISREG"

STDLIB

       Constants
               "EXIT_FAILURE" "EXIT_SUCCESS" "MB_CUR_MAX" "RAND_MAX"

STDIO

       Constants
               "BUFSIZ" "EOF" "FILENAME_MAX" "L_ctermid" "L_cuserid" "TMP_MAX"

TIME

       Constants
               "CLK_TCK" "CLOCKS_PER_SEC"

UNISTD

       Constants
               "R_OK" "SEEK_CUR" "SEEK_END" "SEEK_SET" "STDIN_FILENO" "STDOUT_FILENO"
               "STDERR_FILENO" "W_OK" "X_OK"

WAIT

       Constants
               "WNOHANG" "WUNTRACED"

               "WNOHANG"       Do not suspend the calling process until a child process changes
                               state but instead return immediately.

               "WUNTRACED"     Catch stopped child processes.

       Macros  "WIFEXITED" "WEXITSTATUS" "WIFSIGNALED" "WTERMSIG" "WIFSTOPPED" "WSTOPSIG"

               "WIFEXITED"     "WIFEXITED(${^CHILD_ERROR_NATIVE})" returns true if the child
                               process exited normally ("exit()" or by falling off the end of
                               "main()")

               "WEXITSTATUS"   "WEXITSTATUS(${^CHILD_ERROR_NATIVE})" returns the normal exit
                               status of the child process (only meaningful if
                               "WIFEXITED(${^CHILD_ERROR_NATIVE})" is true)

               "WIFSIGNALED"   "WIFSIGNALED(${^CHILD_ERROR_NATIVE})" returns true if the child
                               process terminated because of a signal

               "WTERMSIG"      "WTERMSIG(${^CHILD_ERROR_NATIVE})" returns the signal the child
                               process terminated for (only meaningful if
                               "WIFSIGNALED(${^CHILD_ERROR_NATIVE})" is true)

               "WIFSTOPPED"    "WIFSTOPPED(${^CHILD_ERROR_NATIVE})" returns true if the child
                               process is currently stopped (can happen only if you specified the
                               WUNTRACED flag to "waitpid()")

               "WSTOPSIG"      "WSTOPSIG(${^CHILD_ERROR_NATIVE})" returns the signal the child
                               process was stopped for (only meaningful if
                               "WIFSTOPPED(${^CHILD_ERROR_NATIVE})" is true)

WINSOCK

       (Windows only.)

       Constants
               "WSAEINTR" "WSAEBADF" "WSAEACCES" "WSAEFAULT" "WSAEINVAL" "WSAEMFILE"
               "WSAEWOULDBLOCK" "WSAEINPROGRESS" "WSAEALREADY" "WSAENOTSOCK" "WSAEDESTADDRREQ"
               "WSAEMSGSIZE" "WSAEPROTOTYPE" "WSAENOPROTOOPT" "WSAEPROTONOSUPPORT"
               "WSAESOCKTNOSUPPORT" "WSAEOPNOTSUPP" "WSAEPFNOSUPPORT" "WSAEAFNOSUPPORT"
               "WSAEADDRINUSE" "WSAEADDRNOTAVAIL" "WSAENETDOWN" "WSAENETUNREACH" "WSAENETRESET"
               "WSAECONNABORTED" "WSAECONNRESET" "WSAENOBUFS" "WSAEISCONN" "WSAENOTCONN"
               "WSAESHUTDOWN" "WSAETOOMANYREFS" "WSAETIMEDOUT" "WSAECONNREFUSED" "WSAELOOP"
               "WSAENAMETOOLONG" "WSAEHOSTDOWN" "WSAEHOSTUNREACH" "WSAENOTEMPTY" "WSAEPROCLIM"
               "WSAEUSERS" "WSAEDQUOT" "WSAESTALE" "WSAEREMOTE" "WSAEDISCON" "WSAENOMORE"
               "WSAECANCELLED" "WSAEINVALIDPROCTABLE" "WSAEINVALIDPROVIDER"
               "WSAEPROVIDERFAILEDINIT" "WSAEREFUSED"