POSIX

(source, CPAN)

version 1.53_01

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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 also Math::Trig.

#acosh

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

#alarm

This is identical to Perl's builtin alarm() function, either for arming or disarming the SIGARLM timer.

#asctime

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

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

and it is called thusly

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

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

#asin

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

#asinh

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

#assert

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

#atan

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

#atanh

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

#atan2

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

#atexit

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

#atof

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

#atoi

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

#atol

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

#bsearch

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

#calloc

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

#cbrt

The cube root [C99].

#ceil

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

#chdir

This is identical to Perl's builtin chdir() function, allowing one to change the working (default) directory, see "chdir" in perlfunc.

#chmod

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

#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.

#CLASSES

#`POSIX::SigAction`

#new

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

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

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

#handler

#mask

#flags

accessor functions to get/set the values of a SigAction object.

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

#safe

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

$sigaction->safe(1);

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

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

#`POSIX::SigRt`

#%SIGRT

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

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

Setting the %SIGRT elements is equivalent to calling this:

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

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

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

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

#SIGRTMIN

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

#SIGRTMAX

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

#`POSIX::SigSet`

#new

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

Create an empty set.

$sigset = POSIX::SigSet->new;

Create a set with SIGUSR1.

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

#addset

Add a signal to a SigSet object.

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

Returns undef on failure.

#delset

Remove a signal from the SigSet object.

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

Returns undef on failure.

#emptyset

Initialize the SigSet object to be empty.

$sigset->emptyset();

Returns undef on failure.

#fillset

Initialize the SigSet object to include all signals.

$sigset->fillset();

Returns undef on failure.

#ismember

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

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

#`POSIX::Termios`

#new

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

$termios = POSIX::Termios->new;

#getattr

Get terminal control attributes.

Obtain the attributes for stdin.

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

Obtain the attributes for stdout.

$termios->getattr( 1 )

Returns undef on failure.

#getcc

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

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

#getcflag

Retrieve the c_cflag field of a termios object.

$c_cflag = $termios->getcflag;

#getiflag

Retrieve the c_iflag field of a termios object.

$c_iflag = $termios->getiflag;

#getispeed

Retrieve the input baud rate.

$ispeed = $termios->getispeed;

#getlflag

Retrieve the c_lflag field of a termios object.

$c_lflag = $termios->getlflag;

#getoflag

Retrieve the c_oflag field of a termios object.

$c_oflag = $termios->getoflag;

#getospeed

Retrieve the output baud rate.

$ospeed = $termios->getospeed;

#setattr

Set terminal control attributes.

Set attributes immediately for stdout.

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

Returns undef on failure.

#setcc

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

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

#setcflag

Set the c_cflag field of a termios object.

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

#setiflag

Set the c_iflag field of a termios object.

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

#setispeed

Set the input baud rate.

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

Returns undef on failure.

#setlflag

Set the c_lflag field of a termios object.

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

#setoflag

Set the c_oflag field of a termios object.

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

#setospeed

Set the output baud rate.

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

Returns undef on failure.

#Baud rate values

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

#Terminal interface values

TCSADRAIN TCSANOW TCOON TCIOFLUSH TCOFLUSH TCION TCIFLUSH TCSAFLUSH TCIOFF TCOOFF

#c_cc field values

VEOF VEOL VERASE VINTR VKILL VQUIT VSUSP VSTART VSTOP VMIN VTIME NCCS

#c_cflag field values

CLOCAL CREAD CSIZE CS5 CS6 CS7 CS8 CSTOPB HUPCL PARENB PARODD

#c_iflag field values

BRKINT ICRNL IGNBRK IGNCR IGNPAR INLCR INPCK ISTRIP IXOFF IXON PARMRK

#c_lflag field values

ECHO ECHOE ECHOK ECHONL ICANON IEXTEN ISIG NOFLSH TOSTOP

#c_oflag field values

OPOST

#PATHNAME CONSTANTS

#Constants: _PC_CHOWN_RESTRICTED _PC_LINK_MAX _PC_MAX_CANON _PC_MAX_INPUT _PC_NAME_MAX _PC_NO_TRUNC _PC_PATH_MAX _PC_PIPE_BUF _PC_VDISABLE

#POSIX CONSTANTS

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

#SYSTEM CONFIGURATION

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

#ERRNO

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

#FCNTL

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

#FLOAT

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

#FLOATING-POINT ENVIRONMENT

#Constants: FE_DOWNWARD FE_TONEAREST FE_TOWARDZERO FE_UPWARD on systems that support them.

#LIMITS

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

#LOCALE

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

#MATH

#Constants

HUGE_VAL

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

#SIGNAL

#Constants: SA_NOCLDSTOP SA_NOCLDWAIT SA_NODEFER SA_ONSTACK SA_RESETHAND SA_RESTART SA_SIGINFO SIGABRT SIGALRM SIGCHLD SIGCONT SIGFPE SIGHUP SIGILL SIGINT SIGKILL SIGPIPE SIGQUIT SIGSEGV SIGSTOP SIGTERM SIGTSTP SIGTTIN SIGTTOU SIGUSR1 SIGUSR2 SIG_BLOCK SIG_DFL SIG_ERR SIG_IGN SIG_SETMASK SIG_UNBLOCK

#STAT

#Constants: S_IRGRP S_IROTH S_IRUSR S_IRWXG S_IRWXO S_IRWXU S_ISGID S_ISUID S_IWGRP S_IWOTH S_IWUSR S_IXGRP S_IXOTH S_IXUSR
#Macros: S_ISBLK S_ISCHR S_ISDIR S_ISFIFO S_ISREG

#STDLIB

#Constants: EXIT_FAILURE EXIT_SUCCESS MB_CUR_MAX RAND_MAX

#STDIO

#Constants: BUFSIZ EOF FILENAME_MAX L_ctermid L_cuserid 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)

CONTENTS

#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

#`POSIX::SigAction`

#`POSIX::SigRt`

#`POSIX::SigSet`

#`POSIX::Termios`