perl核心模块解析（一）    POSIX

详细文档链接如下

源自：http://blog.csdn.net/jonathanxqs

转自：http://perldoc.perl.org/POSIX.html

  POSIX/?p?z?ks/, 是可移植操作系统接口（Portable Operating System Interface ），POSIX标准定义了操作系统应该为应用程序提供的接口标准，是IEEE为要在各种UNIX操作系统上运行的软件而定义的一系列API标准的总称，其正式称呼为IEEE 1003，而国际标准名称为ISO/IEC 9945。

POSIX

• NAME
• SYNOPSIS
• DESCRIPTION
• CAVEATS
• FUNCTIONS
• CLASSES
  • POSIX::SigAction
  • POSIX::SigRt
  • POSIX::SigSet
  • POSIX::Termios
• PATHNAME CONSTANTS
• POSIX CONSTANTS
• SYSTEM CONFIGURATION
• ERRNO
• FCNTL
• FLOAT
• FLOATING-POINT ENVIRONMENT
• LIMITS
• LOCALE
• MATH
• SIGNAL
• STAT
• STDLIB
• STDIO
• TIME
• UNISTD
• WAIT

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 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.

• 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 alsoMath::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.

• 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 $ydaydefault 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 alsoMath::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 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 alsoMath::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.

• 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.

• 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, seechdir.

• chmod

  This is identical to Perl‘s builtin chmod() function, allowing one to change file and directory permissions, seechmod.

• chown

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

• 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.

• closedir

  This is identical to Perl‘s builtin closedir() function for closing a directory handle, see closedir.

• cos

  This is identical to Perl‘s builtin cos() function, for returning the cosine of its numerical argument, see cos. 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 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 andlocaltime.

• cuserid

  Get the login name of the owner of the current process.

  	$name = POSIX::cuserid();

• 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 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.

• execle

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

• execlp

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

• execv

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

• execve

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

• execvp

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

• exit

  This is identical to Perl‘s builtin exit() function for exiting the program, see exit.

• exp

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

• 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, seeabs.

• fclose

  Not implemented. Use method IO::Handle::close() instead, or see close.

• fcntl

  This is identical to Perl‘s builtin fcntl() function, see fcntl.

• fdopen

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

• feof

  Not implemented. Use method IO::Handle::eof() instead, or see eof.

• 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.

• fgetpos

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

• fgets

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

• fileno

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

• 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.

• 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.

• fork

  This is identical to Perl‘s builtin fork() function for duplicating the current process, see fork 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].

• fprintf

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

• fputc

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

• fputs

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

• fread

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

• free

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

• freopen

  Not implemented. freopen() is C-specific, see open 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.

• fsetpos

  Not implemented. Use method IO::Seekable::setpos() instead, or seek seek.

• 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.

• fwrite

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

• getc

  This is identical to Perl‘s builtin getc() function, see getc.

• getchar

  Returns one character from STDIN. Identical to Perl‘s getc(), see getc.

• 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 %ENVarray.

• 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, seegetgrgid.

• getgrnam

  This is identical to Perl‘s builtin getgrnam() function for returning group entries by group names, seegetgrnam.

• 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.

• getpgrp

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

• 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.

• getpwnam

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

• getpwuid

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

• gets

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

  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.

• 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.

• isalnum

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:alnum:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

  You may want to use the /\w/ construct instead.

• isalpha

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:alpha:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

• isatty

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

• iscntrl

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:cntrl:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

• isdigit

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:digit:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

  You may want to use the /\d/ construct instead.

• 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

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:graph:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

• 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 isnan, isfinite, and fpclassify.

• islower

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:lower:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

  Do not use /[a-z]/ unless you don‘t care about the current locale.

• 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, 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

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:print:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

• ispunct

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:punct:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

• isspace

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:space:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

  You may want to use the /\s/ construct instead.

• isupper

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:upper:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

  Do not use /[A-Z]/ unless you don‘t care about the current locale.

• isxdigit

  Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:xdigit:]]+ $ /x , which you should convert to use instead. The function is deprecated because 1) it doesn‘t handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see Character set modifiers in perlre and Which character set modifier is in effect? in perlre).

  The function returns TRUE if the input string is empty, or if the corresponding C function returns TRUE for every byte in the string.

• 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), seekill.

• labs

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

• 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.

  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 seelocaltime.

• log

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

• 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 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 (likeround), 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.

• 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 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.

• memmove

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

• 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.

• 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, though for mkfifo you mustspecify 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

  Returns not-a-number [C99].

  See also isnan.

• 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 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.

• 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 warnand $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.

• 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.

• putc

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

• putchar

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

• puts

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

• qsort

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

• raise

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

• rand

  Not implemented. rand() is non-portable, see rand 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.

• readdir

  This is identical to Perl‘s builtin readdir() function for reading directory entries, see readdir.

• 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

  This is identical to Perl‘s builtin unlink() function for removing files, see unlink.

• 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.

• 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.

• rint

  Identical to lrint.

• rmdir

  This is identical to Perl‘s builtin rmdir() function for removing (empty) directories, see rmdir.

• 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.

• setlocale

  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" );

• 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 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

  A third argument is also passed to the handler, which contains a copy of the raw binary contents of thesiginfo 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 sigactionand possibly also siginfo documentation.

• siglongjmp

  Not implemented. siglongjmp() is C-specific: use die 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 andoldsigset 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.

• sigsuspend

  Install a signal mask and suspend process until signal arrives. This uses POSIX::SigSet objects for thesignal_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. See also Math::Trig.

• sinh

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

• sqrt

  This is identical to Perl‘s builtin sqrt() function. for returning the square root of the numerical argument, seesqrt.

• srand

  Give a seed the pseudorandom number generator, see srand.

• 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 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.

• 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, theresults 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‘sstrftime() 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.

• 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 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.

• 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 .

  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.

• 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 supplystrtoul() 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.

• 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.

• tan

  This is identical to the C function tan() , returning the tangent of the numerical argument. See alsoMath::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.

• 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

  Returns a name for a temporary file.

  	$tmpfile = POSIX::tmpnam();

  For security reasons, which are probably detailed in your system‘s documentation for the C library tmpnam()function, this interface should not be used; instead see 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, see lc, 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, 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 variableTZ , 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.

• 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.

• utime

  This is identical to Perl‘s builtin utime() function for changing the time stamps of files and directories, seeutime.

• vfprintf

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

• vprintf

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

• vsprintf

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

• wait

  This is identical to Perl‘s builtin wait() function, see wait.

• waitpid

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

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

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 thesa_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 thePOSIX::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 existson 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 $rtsigranges 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

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 ECANCELEDECHILD ECONNABORTED ECONNREFUSED ECONNRESET EDEADLK EDESTADDRREQ EDOM EDQUOT EEXIST EFAULT EFBIGEHOSTDOWN EHOSTUNREACH EIDRM EILSEQ EINPROGRESS EINTR EINVAL EIO EISCONN EISDIR ELOOP EMFILE EMLINKEMSGSIZE ENAMETOOLONG ENETDOWN ENETRESET ENETUNREACH ENFILE ENOBUFS ENODATA ENODEV ENOENT ENOEXECENOLCK ENOLINK ENOMEM ENOMSG ENOPROTOOPT ENOSPC ENOSR ENOSTR ENOSYS ENOTBLK ENOTCONN ENOTDIRENOTEMPTY ENOTRECOVERABLE ENOTSOCK ENOTSUP ENOTTY ENXIO EOPNOTSUPP EOTHER EOVERFLOW EOWNERDEAD EPERMEPFNOSUPPORT EPIPE EPROCLIM EPROTO EPROTONOSUPPORT EPROTOTYPE ERANGE EREMOTE ERESTART EROFS ESHUTDOWNESOCKTNOSUPPORT 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_UNLCKF_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_EXPDBL_MIN_EXP FLT_DIG FLT_EPSILON FLT_MANT_DIG FLT_MAX FLT_MAX_10_EXP FLT_MAX_EXP FLT_MINFLT_MIN_10_EXP FLT_MIN_EXP FLT_RADIX FLT_ROUNDS LDBL_DIG LDBL_EPSILON LDBL_MANT_DIG LDBL_MAXLDBL_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_CANONMAX_INPUT MB_LEN_MAX NAME_MAX NGROUPS_MAX OPEN_MAX PATH_MAX PIPE_BUF SCHAR_MAX SCHAR_MIN SHRT_MAXSHRT_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_PIM_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 SIGALRMSIGCHLD SIGCONT SIGFPE SIGHUP SIGILL SIGINT SIGKILL SIGPIPE SIGQUIT SIGSEGV SIGSTOP SIGTERM SIGTSTPSIGTTIN SIGTTOU SIGUSR1 SIGUSR2 SIG_BLOCK SIG_DFL SIG_ERR SIG_IGN SIG_SETMASK SIG_UNBLOCK

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_IXGRPS_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 L_tmpname 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)