POSIX(3pm)

Perl Programmers Reference Guide

POSIX(3pm)

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".

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

"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 = -1)

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", "yday", and "isdst" parameters are all ignored.

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 given arguments are made consistent as though by calling mktime() before calling your system's strftime() function, except that the "isdst" value is not affected, so that the returned value will always be as if the locale doesn't have daylight savings time.

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"

2024-07-03

perl v5.40.0

Source file:	POSIX.3pm.en.gz (from perl-doc 5.40.0-2.1)
Source last updated:	2024-07-03T07:31:26Z
Converted to HTML:	2024-11-21T01:50:01Z