POSIX

(source, CPAN)

version 2.23

You are viewing the version of this documentation from Perl 5.41.6. This is a development version of Perl.

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

#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;

    my $sess_id = POSIX::setsid();

    my $fd = POSIX::open($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.

The notation [C99] indicates functions that were added in the ISO/IEC 9899:1999 version of the C language standard. Some may not be available on your system if it adheres to an earlier standard. Attempts to use any missing one will result in a fatal runtime error message.

#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. Added in Perl v5.22.

#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.

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

#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. Added in Perl v5.22.

#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. Added in Perl v5.22.

#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]. Added in Perl v5.22.

#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 "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! Prior to Perl 5.28 or on a system that does not support thread-safe locale operations, 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. This warning does not apply on unthreaded builds, or on perls where ${^SAFE_LOCALES} exists and is non-zero; namely Perl 5.28 and later compiled to be locale-thread-safe.

This function modifies and queries the program's underlying locale. Users of this function should read 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, and locale-dependent functions within the POSIX module ARE always affected by the current locale.)

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. Added in Perl v5.24.

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

See "nan" for more discussion about NaN.

#setpayloadsig

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

Like "setpayload" but also makes the NaN signaling. Added in Perl v5.24.

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, since Perl v5.24.

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]. Added in Perl v5.22.

#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 its numerical argument -- except that POSIX::sin() must be provided with an explicit value (rather than relying on an implicit $_):

$sine = POSIX::sin(3);    # good

$sine = POSIX::sin();     # throws exception

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 -- except that POSIX::sqrt() must be provided with an explicit value (rather than relying on an implicit $_):

$square_root = POSIX::sqrt(3);    # good

$square_root = POSIX::sqrt();     # throws exception

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.

Note also that it doesn't make sense for a string to be encoded in one locale (say, ISO-8859-6, Arabic) and to collate it based on another (like ISO-8859-7, Greek). The results will be essentially meaningless.

#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 based on the current underlying locale of the program (except for any daylight savings time). Returns the string.

Synopsis:

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

The month (mon) begins at zero, e.g., January is 0, not 1. The year (year) is given in years since 1900, e.g., the year 1995 is 95; the year 2001 is 101. Consult your system's strftime() manpage for details about these and the other arguments.

The wday and yday parameters are both ignored. Their values are always determinable from the other parameters.

isdst should be 1 or 0, depending on whether or not daylight savings time is in effect for the given time or not.

If you want your code to be portable, your format (fmt) argument should use only the conversion specifiers defined by the ANSI C standard (C99, 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 arguments, except for isdst, are made consistent as though by calling mktime() before calling your system's strftime() function. To get correct results, you must set isdst to be the proper value. When omitted, the function assumes daylight savings is not in effect.

The string for Tuesday, December 12, 1995 in the C locale.

$str = POSIX::strftime( "%A, %B %d, %Y",
			 0, 0, 0, 12, 11, 95, 2 );
print "$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_NUMERIC settings, regardless of whether or not it is called from Perl code that is within the scope of use locale. Prior to Perl 5.28, or when operating in a non thread-safe environment, it should not be used in a threaded application unless it's certain that the underlying locale is C or POSIX. This is because it otherwise changes the locale, which globally affects all threads simultaneously.

To parse a string $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 with eq or cmp as an alternative to "strcoll".

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

Unlike the libc strxfrm, this allows NUL characters in the input $src.

It doesn't make sense for a string to be encoded in one locale (say, ISO-8859-6, Arabic) and to collate it based on another (like ISO-8859-7, Greek). Perl assumes that the current LC_CTYPE locale correctly represents the encoding of $src, and ignores the value of LC_COLLATE.

#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]. Added in Perl v5.22.

#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 );

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

#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

Added in Perl v5.28:

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

Added in Perl v5.22:

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

Added in Perl v5.24:

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_ISLNK S_ISREG S_ISSOCK

#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

Added in Perl v5.24:

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

CONTENTS

#NAME

#SYNOPSIS

#DESCRIPTION

#CAVEATS

#FUNCTIONS

#CLASSES

#POSIX::SigAction

#POSIX::SigRt

#POSIX::SigSet

#POSIX::Termios

#PATHNAME CONSTANTS

#POSIX CONSTANTS

#RESOURCE CONSTANTS

#SYSTEM CONFIGURATION

#ERRNO

#FCNTL

#FLOAT

#FLOATING-POINT ENVIRONMENT

#LIMITS

#LOCALE

#MATH

#SIGNAL

#STAT

#STDLIB

#STDIO

#TIME

#UNISTD

#WAIT

#WINSOCK

#`POSIX::SigAction`

#`POSIX::SigRt`

#`POSIX::SigSet`

#`POSIX::Termios`